Forensic Pathology of Firearm Wounds

Updated: Oct 21, 2015
  • Author: Randall E Frost, MD; Chief Editor: J Scott Denton, MD  more...
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Overview

Overview

A firearm may be generally defined as an assembly of a barrel and action from which a projectile is propelled through the deflagration (rapid burning) of a propellant (gunpowder). [1] As injuries due to firearms are common in most areas of the United States, skill in the interpretation of these injuries is vitally important for the practitioner of forensic pathology. 

There are many unique features of firearms that may be of critical importance in a forensic investigation. Although the forensic pathologist need not be an expert on all types of firearms, he or she must be familiar with the basic operation of different weapons in order to interpret the injuries resulting from them. For example, knowledge about the safety features of a weapon that would have allowed or prohibited its operation in a given set of circumstances may be of great importance in determining the plausibility of a given death scene scenario. Similarly, knowledge of muzzle shapes, size and configuration of a weapon, approximate weight of trigger pull, amount of recoil, and a host of other factors may serve to refute or substantiate a putative explanation for how the injury was sustained.

Historical information

The history of gunshot wounds necessarily parallels that of the development of firearms themselves. A full treatment of the history of arms development would require volumes, but readers interested in the history of firearms or their function are encouraged to seek more information in the suggested reading sources in the Additional Resources section.

Gunpowder is thought to have originated in China during the 9th century, c. 850, but it was not until the mid-13th century that evidence of gunpowder formulas and experimentation began to be found in European writings. Shortly thereafter, instances of the use of cannons in warfare are reported, and the expansion of the use of the firearm as an instrument of war rapidly followed.

Over the centuries, firearms have been progressively refined. Types of lockworks and loading mechanisms have progressed from muzzle-loading matchlocks, flintlocks, and cap-and-ball arms, to modern self-contained metallic cartridges fired from breech-loading firearms.

Throughout this process, firearms have been made more accurate, and rates of fire have progressed from 2 or 3 rounds per minute in the days of muzzle-loaders to many hundreds of rounds per minute in modern automatic weaponry. Muzzle velocities of available cartridges have increased greatly, and bullet technology has been steadily refined. Propellants have been improved, with the most striking improvement being a change from black powder to smokeless powder in the 19th century. In the present day, a wide variety of small arms are available for military and civilian use throughout the world. However, in spite of the dizzying variety of firearms in use, the wounds produced by them have many similarities within some broad categories.

See also the following:

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Modern Small Arms

Modern small arms may be classified generally into handguns, rifles, and shotguns. [2] Automatic weapons (machine guns and submachine guns) may also be included in this classification, but they are less commonly encountered in civilian practice.

A handgun is designed to be held in the hands without any bracing mechanism and generally has a short barrel relative to other types of arms. Handguns may be further divided into revolvers (in which a revolving cylinder contains the cartridges to be fired) and pistols (which include semiautomatic or autoloading weapons firing from a spring-loaded magazine).

Rifles are long-barrelled weapons with a stock designed to be braced against the shoulder of the shooter and a rifled barrel (spiraling parallel grooves cut into the barrel to stabilize bullets). Both of these characteristics serve to increase the practical accuracy of the weapon. In general, rifles are chambered for more powerful ammunition than that found in handguns, although this is not always the case, as many rifles are chambered for rounds that were designed to be fired in handguns, and vice versa. Rifles are available in a variety of action types, including semiautomatic, bolt action, lever action, and single shot, among others.

Shotguns are also long-barrelled weapons, but they have a smooth, nonrifled barrel and usually fire a charge consisting of multiple, round shot instead of a single projectile. Common action types include pump action, semiautomatic, single-shot, and double-barrelled varieties.

Handgun action mechanism types

Typical repeating handgun action types include single-action, double-action, and semiautomatic (also known as autoloading) mechanisms. A single-action firearm has a hammer that must be cocked by the shooter for each pull of the trigger. The typical Colt 1873 "Peacemaker" pattern revolver is a common single-action weapon.

A double-action mechanism allows the operator to cock the hammer of the firearm for each pull of the trigger, but it also allows the weapon to be fired by a single, long trigger pull that simultaneously cocks the hammer and then releases it, discharging the weapon. This action type is well represented by more modern revolver designs that once comprised the majority of the law enforcement handgun market. More recently, this market has come to be dominated by semiautomatic handguns.

When a semiautomatic weapon is fired, the momentum or gas pressure of the discharging bullet/cartridge causes the fired case to be ejected from the firearm, a fresh cartridge to be loaded into the firing chamber, and the weapon to be cocked and readied for firing. Because of this, multiple follow-up shots may be fired quickly without manual reloading or cocking of the firearm. Cartridges are usually fed into the firing mechanism via a spring-loaded magazine that holds multiple rounds. Such magazines are often rapidly interchangeable, facilitating quick reloading of the weapon. In such a weapon, one pull of the trigger will still discharge only a single round. This is in contrast to the fully automatic weapons most commonly found in the hands of police or military agencies. In such firearms, represented by machine guns or submachine guns, multiple shots will be rapidly fired as long as the trigger is depressed.

Firearms cartridges

Modern cartridges for handguns and rifles are composed of a brass or nickel case enclosing a powder charge. A bullet, usually lead or copper-encased lead, sits atop the powder charge and is crimped into the case. At the base of the case is an impact-sensitive primer. The primer is designed to detonate when struck by the firing pin of a firearm, sending a jet of flame into the overlying powder charge and igniting it. Gas formed by the burning of the powder charge produces a rapid increase in pressure within the cartridge case and bore of the firearm, forcing the bullet out of the case and down the barrel of the firearm at great speed.

Ammunition

Bullets may have a variety of shapes and types of construction, but modern commercial ammunition often has a hollow cavity in its nose (a "hollow point") and a copper jacket surrounding much of the lead bullet. The cavity is designed to facilitate expansion of the bullet in tissue, improving terminal ballistic performance and reducing the possibility of completely perforating the target, potentially causing injury to bystanders.

Modern shotgun ammunition has some similarities to the above, except that the metallic case is replaced by a plastic or (less frequently) cardboard shell, within which is enclosed a number of round shot formed typically of lead, steel, or bismuth. These shot are often enclosed in a plastic "cup" designed to protect and enclose the shot charge on its journey down the barrel of the shotgun, falling away after exiting the weapon. In lieu of a shot cup, some shell designs incorporate a felt and/or plastic disc of "wadding" over the powder charge. Shot comes in a variety of sizes, from tiny "birdshot" to much larger "buckshot" pellets. Shotguns are also capable of firing single, large-caliber projectiles known as "slugs."

A more detailed discussion of firearms, ammunition, and their functions is beyond the scope of this article, but, again, excellent discussions may be found in the Additional Resources section.

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Epidemiology

The United States is a nation with a long history and tradition of private firearm ownership rights. There are an estimated 250 million or more privately owned firearms in the United States, and the number generally rises each year. [3]

Data from 2007 from the National Violent Death Reporting System, encompassing 16 states, showed an age-adjusted death rate due to firearms of 9.93 per 100,000 population. During 2006, the Centers for Disease Control and Prevention (CDC) and National Center for Injury Prevention and Control (NCIPC) noted a total of 12,791 firearm deaths due to homicidal violence and 16,883 firearm deaths due to suicide. [4]

The reasons for these injuries, mitigation strategies, and the role of regulation of firearms as a preventative measure have engendered intense and ongoing public debate, particularly in recent decades. Political beliefs notwithstanding, it is clear that all forensic pathologists practicing in the United States will encounter the need to interpret firearm injuries on a regular basis.

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Aspects of Firearm Wounds

The expert medicolegal examination of firearm wounds may allow determination of several aspects of these injuries, including the following [2] :

  • Range of fire
  • Type of weapon used to inflict the injury
  • Trajectory of the missile or projectile
  • Type and extent of the injuries inflicted by the projectile(s)

Range of fire

Range of fire, or muzzle to target distance, may be divided into contact, near contact, intermediate, and distant categories, with various subtypes also demonstrable. Contact and intermediate range wounds are often collectively referred to as close-range wounds.

Determination of range of fire is based on the characteristics of a firearm wound, features of the wound that have been imparted by material issuing from the muzzle of the firearm other than the bullet, or from features due to direct interactions between the target and the firearm itself. Material from the firearm muzzle may take the form of soot, hot gas, gunpowder particles, or other material, and the effects of this material are discussed in more detail below. [5] The range of fire has obvious relevance to such issues as whether a wound is self-inflicted or inflicted by another person, the truth of proffered explanations of shooting events, and the validity of self-defense arguments.

Type of weapon

The general type of weapon may sometimes be determined by the characteristics of a wound, and by the recovery of the projectile causing a wound, with appropriate criminalistic analysis. In addition to determination of bullet caliber (diameter) and type, telltale markings may be present on recovered projectiles or casings, allowing matching of the projectile or case to a firearm. Such markings are created when a bullet or case contacts the barrel rifling, breech face, chamber, ejector, or other parts of a firearm, and they may be sufficiently unique to qualify as "individual characteristics" that allow matching of a recovered bullet or fragment to the specific weapon that fired it. In other cases, only general characteristics such as the likely type or brand of the firearm may be determined, but these features are still useful. The importance and necessity of recovering retained projectiles should be understood, considering the potential wealth of information that may be gleaned from their examination.

Trajectory of the missile or projectile

The trajectory, or direction, of a projectile through the body, may be approximated, but it must be kept in mind that this does not necessarily equate to the trajectory of the bullet through space. Because the bodies of the victim and shooter are not static and may move about in 3 dimensions during a shooting event, the standard anatomic position is utilized to describe the trajectory of a bullet through a body. This assumes by convention that the victim is standing upright, with arms outstretched downward, and with palms facing outward. All directions are given based on this positioning of the body, which is very likely not the actual position the victim was in when shot.

However, occasionally the pathway of a bullet through the body may give some indication of the actual position of the body when shot. For example, a bullet may exit one part of the body (such as an arm) only to re-enter the torso or other body part. This may be suggested by the characteristics of the wounds (see below), as well as the juxtaposition of the 2 wounds on certain positions of the body parts, which can be demonstrated at the time of autopsy examination.

Type and extent of the injuries inflicted by the projectile(s)

The types of injuries caused by firearm wounds have significance above and beyond cause and manner of death determination. The assessment of damage to vital organs, central nervous system components, or bony framework may allow a forensic pathologist to address many issues of legal significance, such as survival time or the time required for a wound to incapacitate a victim. It may also be up to the forensic pathologist to dispel much of the erroneous and mythologic concepts that abound regarding firearm wounds, such as "stopping power," instantaneous death, or bodies being hurled about by bullet impacts (see below).

The study of the interaction of a missile, projectile, or bullet is referred to as terminal ballistics, and it is a field of great importance to clinicians, forensic pathologists, those in law enforcement and military agencies, and others. Much work in this area has been done to attempt to elucidate the effects of a bullet on a victim's body [6, 7, 8, 9, 10] ; many of these efforts have centered on explanation of the 2 primary traumatic effects of a projectile; that is, formation of the permanent and temporary cavities.

When a bullet perforates tissue, it forms a cavity or track that persists and results from crushing and laceration of body tissues. Because of the high velocity of the bullet, it will also form a temporary cavity caused by the sonic shock wave that radiates from the passing projectile. The size and shape of this cavity will be dependent on a number of factors, primarily the velocity of the projectile.

As kinetic energy increases by the square of bullet velocity, a high-velocity projectile will tend to cause a larger temporary cavity than a lower velocity one. Because of this, temporary cavities are usually not significant in handgun injuries, but they are of much greater significance in high-velocity rifle wounds. In addition to velocity, the behavior of a projectile in tissue (eg, stabilized, destabilized, fragmented) will also bear on the size and shape of the cavity. [11] Depending on the elasticity and other characteristics of the tissue in question, the formation of the temporary cavity will have varying effects on the body.

Although there are well-systematized principles that allow for categorization of various types of firearm wounds, all such injuries are, in fact, unique, and exceptional variability may be seen in any large series of wounds. Some injuries defy categorization, and in any such case, the forensic pathologist must honestly assess the wound and the amount of interpretive information that may be extracted from it, without attempts to rigidly "pigeonhole" the wound for the sake of classification. A rigorous assessment of all features of the injury, thorough scene investigation, examination of clothing items of the victim, and examination and understanding of the implicated firearm (if available) provide the best opportunity for correct evaluation of the injury.

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Forensic Investigation of Firearm Deaths

As firearm injuries will fall into the manner of death categories of homicide, suicide, or accident, all will come under the jurisdiction of a medical examiner, coroner, or justice of the peace, depending on the death investigation system in the local area. In addition to local statute, published professional standards require forensic pathologists in such settings to investigate deaths due to violence, which clearly includes firearm wounds. [12] It is not uncommon for a person to survive a firearm wound, eventually succumbing to remote complications of the wound weeks, months, or even years later. However, such a case remains of medicolegal interest if it can be shown to be directly or indirectly related to the initial wound.

Although some authors might question the need for a detailed medicolegal investigation into deaths manifestly due to firearm wounds (after all, "we know why he died, don't we?"), the proper examination of such a case may clarify the cause of death, the identify of the assailant, and the manner of death. These are often areas of contention. Was the firearm wound death a homicide, accident, or suicide? Was the shot fired in self defense? Was the victim attacking or fleeing from the shooter? Was the fatal bullet fired from the accused person's gun? Proper interpretation of trajectory, range of fire, and other findings will help to answer these and many more questions. Recovery of a bullet may serve to exonerate or implicate a particular firearm in the incident. [13]

Because of the seriousness and gravity of the legal questions to be answered, these examinations should be conducted by a physician properly trained and certified in forensic pathology.

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Forensic Scene Examination

The scene examination in the case of a firearm wound victim may provide invaluable information. At the scene, care should be taken not to disturb blood patterns on the floor, as they may give indications as to the site of injury and the degree of activity of the decedent after injury. The position and location of the firearm should be carefully noted, if present, and its position of battery (eg, is the firearm loaded, is a round chambered, are fired rounds in the cylinder, is the weapon cocked) is of primary importance.

A person familiar with the type of weapon in question should recover the firearm and clear it if necessary, taking note of the position of fired casings relative to the hammer of a revolver, the presence or absence of a magazine in a semiautomatic handgun, the slide position or any jams noted in a semiautomatic handgun, and the position of a pump shotgun slide, among other variables. All of this information may have significant bearing on the manner of death determination at a later date.

The type of ammunition present at the scene, either in a firearm or elsewhere, should be described in detail (brand, caliber, bullet style) so that any recovered bullet can be immediately compared with what was found in the firearm at the scene.

Any projectile found beneath the decedent, stuck to clothing, or other areas should be photographed and recovered at that time to prevent the possibility of loss during transport. If firearm primer residue sampling is desired, it may be collected at the scene, or the hands may be covered by paper (not plastic) bags before transport to prevent evidentiary loss during transport.

The presence of bullet strikes on the walls of a room should be noted, as these can serve as reference points for later reconstruction of the position of a shooter when combined with a trajectory through the body.

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Trace Evidence

In evaluating firearm wounds, the decedent's clothing should be examined, if at all possible. [2] The clothing should be examined to attempt to match the defects on it with those on the body, as well as for the presence or absence of residues from the firearm discharge. These residues will predominately take the form of soot or gunpowder particles.

Soot usually appears as a dark gray, featureless deposit surrounding the bullet defect on clothing. It is readily visible on light-colored fabric, but it may be difficult or impossible to discern with the naked eye on dark fabrics. Soot may also be obscured by blood, dirt, or other substances. Blood, in particular, may darken on drying and should not be confused with soot deposition.

Gunpowder particles, contrary to common misconception, are often not dark in color. They frequently have a light color, often with a greenish hue, and may be seen some distance from the bullet perforation, depending on the muzzle to target distance (see below). These particles will have varying shapes, depending on the type of powder in use. Common configurations include ball (or spherical), flattened ball, flake, and cylindrical powders.

Gunpowder grains may be difficult to see with the naked eye; viewing under magnification may assist in identifying and/or confirming the presence of particles. A loupe lens or a handheld dissecting microscope head can be useful in examining such areas. In a case of obvious or possible foul play, garments should be carefully air dried, placed in individual paper bags, and either submitted for further criminalistic examination or retained for potential future examination as required.

If a bullet has passed through an intermediary target before striking the decedent, fragments of that target may be adherent to clothing or the surface of the body. Small fragments of lead or copper jacket material may also be found in a similar circumstance, due to break-up of the bullet. A "plug" of fabric or other such material may be found within the cavity of a hollow-point bullet that has passed through clothing, a pillow, a car seat, or other objects.

Naturally, examination of the decedent for other "trace" evidence, in addition to that associated with firearm wound assessment, may be performed as appropriate. This might include fingernail clippings, sexual assault swabs, hair combings, or collection of any other needed materials.

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Gross Examination and Findings

All wounds should be carefully examined before cleaning of the body, as should the hands. Soot and other residues on the body may be washed away with cleaning, and they may only be seen on initial inspection of the victim. Photographs of a wound before and after cleaning may be valuable for the documentation of such findings.

Localization and measurement of wound(s)

The wound(s) should be localized on the body. Measurements to locate a wound may be taken from the top of the head and right or left of the midline of the body, but other datum points may be used as well. Use of a consistent reference point will allow reconstruction of wound trajectories, which is the primary reason for taking such measurements.

In addition to giving the precise measured location of a wound, its location should also be generally described using easily identifiable anatomic landmarks. For example, a firearm wound of the chest might be described as "36 cm from the top of the head, 4 cm left of midline, and above and medial to the left nipple."

Next, the wound itself should be measured, generally in 2 dimensions (eg, 0.5 X 0.7 cm) and described by its shape (eg, round, oval, slitlike, stellate, ragged). The presence or absence of any abrasion rim should be noted, with its width and extent measured. Any soot or powder stippling should be noted, and its extent measured as well (see below).

External wounds versus number of internal bullets/projectiles

Before commencing the autopsy of a firearm injury victim, it is important to compare the wounds noted externally with the number of bullets or projectiles found in the body on radiographic examination. Because a bullet may either exit the body, producing both entrance and exit wounds (perforating), or remain in the body, producing only an entrance wound (penetrating), the number of wounds plus the number of bullets found on radiographs should generally be an even number. If there is a discrepancy, consideration should be given to the possibility of missed wounds (check the mouth, perineum, axillae, gluteal cleft, and other "hidden" spots), missed projectiles (increase the extent of the radiologic examination), or separation of bullets into core and jacket fragments within the body (1 entrance wound resulting in 2 "projectiles" seen radiographically).

It is possible for a small-caliber bullet to enter the heart or a large blood vessel and be subsequently embolized or pumped "downstream" for some distance by cardiovascular action. [14] If surgery has been performed, consider that a bullet may have been purposely or inadvertently removed during the procedure. Small-caliber projectiles may be picked up by accident with a sponge, dropped, or suctioned away. It is also possible that multiple "entrance wounds" may have been produced by fragmentation of a projectile or an intermediary target (see below), or that "exit wounds" may have been produced by bone fragments instead of a bullet.

Autopsy documentation

In preparing an autopsy report in cases of firearm wounds, it is preferable to describe each separate firearm wound in its entirety, rather than describing all entrance wounds, then all exit wounds, and then internal injuries. For example, a firearm would best be documented by describing the location, size, and character of the entrance wound, then the path of the wound through the body, and finally, the recovered projectile or exit wound (size, location, description).

Associated findings, such as hemothoraces, may then be mentioned, followed by an approximate direction of the wound track, using the standard anatomic position as a reference point. As an example, a wound path may be described as "front to back, left to right, and slightly downward."

The assignment of a numeric angle measurement to the wound track should be discouraged, as this presents a false level of precision to the reader of the report—and, potentially, to a jury. The overriding concern in such a report is that the description must paint a picture of the wound as observed by the forensic pathologist so that it may be clearly understood by the reader.

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Special Dissections

It is important to attempt to develop a preliminary idea of wound pathways and entrance versus exit wounds before commencing the internal examination of the body. This is, of course, subject to change as the examination commences and may not be possible in all cases. Removal of organs should be delayed until all wound tracks have been identified, if possible, because evisceration irreversibly alters many anatomic relationships, rendering further analysis of tracks difficult.

Blood accumulations should be measured as an adjunct to determining the mechanism of death, time of survival, and likelihood of survival, among other determinations. Other findings, such as major heart or vascular injury, blood aspiration, or cardiac air embolus, may assist in addressing these questions at a later date.

If a projectile enters the spine, it is important to open the spinal canal and examine the spinal cord to determine the presence or absence of cord damage, as activity of the shooting victim after injury is often a matter of question in court. For the same reason, damage of the brain, supporting axial skeleton, and extremities should be documented with the intent of addressing potential questions about consciousness, locomotion, or ability to fight.

Although a single firearm wound may be easily tracked through the body, the presence of multiple wounds may present problems in analysis, particularly if the wound tracks intersect, the decedent was shot with a small-caliber weapon, or if intermediary targets caused the projectiles to fragment. In some cases, the wound track cannot be determined to an acceptable degree of certainty. In such cases, it is important for the pathologist to honestly state so in the autopsy report.

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Radiography

The clothed body of a firearm wound victim should always be thoroughly radiographed. All parts of the body affected by a firearm wound must be imaged, and it may be that even sites distant from the entrance wound need to be examined. For example, a firearm wound of the shoulder can pass through the arm, chest, and abdomen, terminating in the decedent's leg under certain circumstances. Some modern full-body x-ray scanners, such as the Lodox machine, can provide high-resolution full-body radiographs in a minimum amount of time, making this process much more efficient and complete.

If appropriate bullets or fragments are not found in initial radiographs, repeat images of other body areas should be obtained, taking care to cover all areas of soft tissue and clothing. This is particularly important in obese decedents, in whom more than one x-ray plate may be needed to fully image a level of the torso. Such individuals may require a longer exposure or higher kilovoltage (kV) of the x-ray beam to obtain adequate visualization. Lateral views of retained projectiles will be of tremendous assistance in localization of the bullet in many cases.

When discussing firearm radiography, it is important to remember that magnification effects may make projectiles and fragments appear to be much larger than their actual size (see the following image). For this reason, one should never attempt to estimate the caliber of a projectile from a radiograph without appropriate consideration of the focal length of the x-ray tube and the distance from the imaged projectile to the x-ray plate. [15]

Radiograph showing identical projectiles with diff Radiograph showing identical projectiles with different apparent dimensions due to a magnification effect. One projectile is in the tissues of the anterior body, whereas the other is posterior.

The pathologist should also be aware that some exotic ammunition may have bullet components that are less visible on radiographs than typical lead or copper bullets and jackets. These may include aluminum bullet jackets, plastic sabots or caps, or other components.

Some forensic pathologists have found fluoroscopy to be useful in localizing projectiles within the body, although this technique is far less common than standard radiography.

A few centers have been fortunate enough to have computed tomography (CT) scanning equipment available for examinations of decedents, and this technique has great potential for research. At this time, however, CT scanning of decedents remains expensive and is not readily available enough for routine use. [16, 17]

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Special Handling

It is of critical importance that recovered evidence in firearm wound cases be properly handled.

Clothing items should be spread out or hung up and allowed to air dry before being individually placed in paper bags for retention or crime laboratory examination.

The handling of bullets or other evidence will vary somewhat according to locales, and pathologists should consult with their local law enforcement agencies or crime laboratories to determine specific procedures for evidence handling. However, in general, bullets or fragments removed from a decedent should be gently rinsed (in plain water; do not use soaps or bleach) to remove blood and excess tissue, then dried, wrapped in clean absorbent paper, and placed in an evidence envelope with appropriate labeling of the source of the bullet, case number, and other information. The envelope should be sealed with evidence tape and signed by the pathologist, then transported to the appropriate law enforcement agency or crime laboratory using a documented chain of custody.

In the past, it was customary for the pathologist removing a bullet to engrave his/her initials or some type of code onto the base of a removed bullet before releasing it. In theory, this would allow the pathologist to later definitively identify the bullet at trial. In fact, however, this procedure does not guarantee that the bullet is properly identified, and in practice, such engraving is exceedingly difficult to perform on a small projectile or to visualize when seated in a dimly lit courtroom. The best guarantee of the authenticity of the firearms evidence is a well-documented chain of custody. Some pathologists have found it helpful to photograph each removed projectile next to the labeled envelope into which it is to be placed, but even this is no assurance of authenticity in and of itself.

Shot cups or wadding from a shotgun wound should be recovered, rinsed, and dried, then handled in a manner similar to that noted above. Felt wads may be saturated with blood and body fluids and thus should be allowed to dry before packaging. When dealing with shotgun wounds due to birdshot, there may be innumerable pellets in the body, and recovery of all the pellets is impractical. In such cases, a sampling of representative pellets should be recovered (a dozen or so would usually suffice).

In the case of rifle wounds or handgun wounds with extensive fragmentation of the projectile(s), large fragments should be recovered. However, it may not be possible or practical to recover all tiny fragments from a wound, nor are these of any compelling forensic interest in most cases. It should be remembered that magnification effects may cause a very tiny fragment to seem deceptively large on radiographs.

It is important to avoid contacting bullets or large fragments with metallic objects such as probes, forceps, or scalpel blades. Because the potential exists to examine the bearing surfaces of a bullet for comparison purposes, scratches or other marks inadvertently placed on such a surface could potentially interfere with criminalistic examination.

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Microscopic Examination and Findings

Although the microscopic appearance of firearm wounds has been studied and described, [18] the histology of firearm wounds rarely provides much meaningful information to the forensic pathologist. [19] Wounds will show crush of tissue with hemorrhage, and if the interval between injury and death is sufficiently long, typical healing changes will be evident. Soot and powder grains may be seen, particularly in the case of contact wounds, which will also show superficial thermal alteration of the tissues (see the image below).

Photomicrograph of soot in the tissues of an entra Photomicrograph of soot in the tissues of an entrance wound.

The histologic presence of soot or powder grains within a wound track should not be used to infer information regarding range of fire, as soot or powder may be carried into a wound by a projectile fired from a long distance. In fact, soot can sometimes be seen histologically in sections from a firearm exit wound. Range of fire determinations should be made on the basis of gross examination.

The use of bullet cytology has been reported in the literature. [20] In such cases, bullets are rinsed in an appropriate buffer solution, and cytologic preparations are prepared from the fluid. Although potentially useful in some situations, this procedure is not commonly utilized in practice. It is also possible to identify nonorganic material from intermediary targets on the surface of a bullet that has passed through that material. Electron microscopy with elemental analysis has been utilized for such purposes or for characterizing tiny metallic fragments or metallic deposits on bone.

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Photographic Documentation

Photographic documentation is of critical importance in the examination of firearm wounds, as it not only allows for secondary review of the autopsy by consultants or opposing experts but also allows the autopsy physician a chance for further review and/or consideration after completion of the examination. The National Association of Medical Examiners Forensic Autopsy Standards (NAME) [12] and Accreditation Checklist [21] criteria require that photographs be taken in the case of significant injuries. Photographs should be of high quality, such that an observer can readily distinguish salient characteristics of the wound from the images.

In general, photographs of wounds before cleaning are difficult to interpret and should be avoided. However, overall photographs of a victim before undressing and cleaning can provide useful information about things such as blood droplet patterns, position of clothing, and other information, and may be useful. If soot is noted around a wound, it should be photographed before cleaning, as soot may be removed in the cleaning process.

In other cases, the body should be cleaned, wiped dry, and all extraneous items (towels, scalpels, or other instruments) removed from the field before photography. Overall photographs showing the location of the wound(s) on the body should be taken, followed by close-up photographs of each wound. If scales are utilized, they should be in the same plane as the wound itself and should be placed unobtrusively at the edge of the photograph. Similarly, if an identifying case number is in the photograph, it too should be at the edge of the photograph in an unobtrusive manner.

If wounds are in a hair-bearing area such that they are obscured by overlying hair, the area should be carefully shaved to allow adequate examination of the wound and photodocumentation (see the following image). Examination and photography should take place immediately after shaving, because tiny nicks caused by shaving may mimic stippling once drying takes place.

It is often difficult to discern much useful information from photographs of internal findings owing to bloody fields and the difficulty of reducing complex 3-dimensional pathways to 2-dimensional photographs. If photographs of internal findings are used, great care must be taken to clean the field and remove as much residual blood and other matter as possible to avoid distractions in the photograph. Pointers and clearly definable anatomic points of reference may be included in the photographs to assist in interpretation.

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Primer Residues

In addition to those residues deposited on the clothing or skin due to discharge of a firearm, gunshot primer residues may also be deposited. These are generated by the discharge of the cartridge primer, which vaporizes the metallic compounds within that primer and causes them to be discharged as a cloud around the firearm. These compounds are most commonly barium, lead, and antimony, although not all are present in every brand or type of primer.

The primer residues may be collected by swabbing or using tape to lift them from the skin surfaces and then testing for the residues by various laboratory means, usually scanning electron microscopy/energy dispersive x-ray spectroscopy (SEM-EDX) or inductively coupled plasma atomic emission spectroscopy (ICP-AES). The testing of primer residues is more properly considered in a dissertation related to criminalistics, but the interpretation of the residues is an area often posed to the forensic pathologist.

Traditionally, it was felt that the distribution of residues on the decedent's hands could help to discern whether a gunshot wound was self-inflicted or not. The premise was that in a self-inflicted wound, residues would be deposited on the back of the firing hand, because the palm that was grasping the firearm would be "protected" or shielded by its position. However, in an assault situation, a victim would put his or her hand(s) up instinctively to shield himself or herself, allowing primer residues to be deposited on the palms. [2]

The problem with this view is that the cloud of gunshot primer residue is widely distributed in the area of a discharging firearm and may settle on any convenient surface, even those several feet from the firearm. This would include any body surfaces of the decedent, as well as those of the assailant. Firearms themselves are often contaminated with primer residues, as would be expected, such that anyone picking up such a gun would be expected to have residues on his/her palm.

In practice, the presence or absence of primer residues on the hands have limited utility in the determination of manner of death in postmortem cases. [22, 23]

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General Principles of Wound Interpretation

Various types of firearms may produce wounds that have different characteristics reflective of the type of weapon inflicting the injury. However, many characteristics of firearm wounds are similar across the range of weapons. We will first discuss these basic characteristics, which are, in general, associated with handgun wounds. For a much more detailed treatment of this topic, the reader is referred to the classic textbook on the subject by DiMaio. [2]

Entrance wounds

Firearm entrance wounds are typically round to oval, with smooth edges and a zone of epidermal abrasion surrounding the wound edge. This abrasion is caused by the rubbing or scraping of surrounding skin surfaces by the bullet as it indents the skin before perforating it. If the bullet strikes perpendicular to the skin, the abrasion will be of uniform width around the wound, as seen in the image below.

Entrance gunshot wound with a thin, evenly distrib Entrance gunshot wound with a thin, evenly distributed abrasion rim.

If the bullet strikes the skin at an angle other than perpendicular, the abrasion will be widest along the margin from whence the bullet came (toward the muzzle of the firearm). See the following images.

Entrance wound with an eccentric abrasion rim indi Entrance wound with an eccentric abrasion rim indicating that the bullet struck the skin obliquely. In this case, the bullet was traveling in an upward direction.
Gunshot wound with extremely eccentric marginal ab Gunshot wound with extremely eccentric marginal abrasion. The bullet traveled from the direction of the left upper margin of the photograph.

It must be kept in mind that the distinction of entrance versus exit wounds is not always a simple matter. With the exception of contact and intermediate range wounds, no single feature of a firearm wound of entrance (eg, shape, abrasion, size) is necessarily diagnostic of an entrance wound. Rather, the totality of the wound features should be considered to differentiate between entrance and exit wounds. It should also be noted that caliber of an impacting projectile cannot be reliably determined from the size of an entrance wound on the skin.

Distant/indeterminate wounds

If the muzzle of the firearm is more than a few feet from the skin, there will be no residues of any kind deposited on the body surrounding the firearm wound. This type of wound is classified as a distant wound. Some practitioners refer to these as "indeterminate" wounds, based on the concept that one cannot entirely rule out the possibility that the wound was produced by firing at close range through an intermediate target that screened the firearm residues from the skin. This should, of course, be considered as a possibility during examination of death scenes and the body of a firearm wound victim.

Hard contact wounds, stellate wounds, and muzzle imprints

The discharge of copious amounts of hot gas, soot, unburned, or partially burned powder particles, metallic fragments, or other debris from the muzzle of a firearm, along with the bullet may result in characteristic findings on the skin or clothing of a firearm wound victim. When the muzzle of a firearm is held firmly against the skin of a victim as it is fired, a hard contact wound results. In this wound, a dark zone of soot (carbon) deposition is present around the edge of the entrance wound, as shown in the image below. This soot is seared into the skin by hot gases exiting the firearm muzzle and cannot be completely washed away from the wound. It may also be possible to discern a cherry red color of the underlying soft tissues due to the carboxyhemoglobin formed when carbon monoxide that is formed from the burning powder charge is injected into the tissues with the muzzle blast.

Contact gunshot wound with a margin of seared soot Contact gunshot wound with a margin of seared soot.

If the muzzle of a firearm is held firmly against the skin overlying a flat bony surface, such as the skull, a stellate wound may result. This irregular wound may be quite large and results from gases expelled from the firearm dissecting beneath the skin of the wound, with resultant explosive rupture of the skin as the gas expands. Although such a large and irregular wound is often misinterpreted by untrained individuals as an exit wound, the large quantities of soot often present within the wound and on the underlying skull should be a clue to its true nature (see the following image).

Stellate hard contact wound of the head. Note the Stellate hard contact wound of the head. Note the abundant soot in the wound depths.

The same process of gas expansion beneath the skin may result in a muzzle imprint . In a contact firearm wound, gas may dissect beneath the skin and cause it to expand or "balloon" outward, forcibly impacting the muzzle of the impinging firearm. This results in an impact abrasion that may partially or fully replicate the configuration of the firearm muzzle (see the first image below). The actual wound defect may also have a stellate appearance if it is over the skull (see the second image below).

Imprint showing the shape of a firearm muzzle and Imprint showing the shape of a firearm muzzle and sight.
Hard contact gunshot wound with a stellate appeara Hard contact gunshot wound with a stellate appearance and muzzle imprint.

Another contact firearm wound phenomenon results in a radial strip of soot and seared skin that extends from the edge of a firearm wound. Various explanations for the phenomenon have been offered, but it may result when, after the bullet enters the body, the muzzle of the gun slides across the skin for a brief instant as hot gas and soot continue to issue from the muzzle. This may result in "painting" a strip of soot and/or searing radially from the wound (see the following image).

Strip of soot and underlying searing extending rad Strip of soot and underlying searing extending radially from a gunshot wound.

Another explanation for this phenomenon of a radial strip of soot and radially extending seared skin is that it represents an incomplete contact wound, resulting from a partial break in contact between the muzzle of the firearm and the skin, allowing a jet of hot gas to extend outward from the wound. However, in most wounds, the area of soot deposition and burning might be expected to be fan-shaped as opposed to bandlike. This process appears to be particularly common with .22 caliber rimfire rifles, but it is also noted it in larger-caliber handguns.

Muzzle compensators or muzzle brakes may also produce characteristic findings on the skin around a wound. These are devices on the muzzle of a firearm that direct gas upward and perpendicularly (usually) from the barrel of the gun to help limit muzzle rise and attenuate recoil. Such a compensator may consist of 2 slots milled into the barrel and/or slide of a pistol or other firearm, allowing gas to issue in a radial fashion from each side of the upper edge of the muzzle end of the firearm on firing. This may result in marking (with searing and/or soot deposition) the skin around the wound in a "V" shape. Similar marks may be seen from flash suppressors on rifle or shotgun barrels. In the case of flash suppressors, the radial burns may extend from multiple points around the wound, depending on the type of suppressor installed. See the images below.

Compensator burn from a contact gunshot wound. Compensator burn from a contact gunshot wound.
Distinctive mark from a hard contact wound due to Distinctive mark from a hard contact wound due to a shotgun with a muzzle brake.

Loose/near contact wounds

When the barrel of a firearm is held in loose contact with the skin or up to a few centimeters away, soot may be deposited loosely on the skin (see the following image). The soot from this loose-contact or near-contact wound is not seared in place like that of a hard contact wound, and it may be largely washed away during cleaning of blood from the wound. Consequently, examination and photographic documentation should take place before cleaning. Once this has been done, gentle cleaning of the wound with warm water and very light scrubbing may serve to remove obscuring blood while leaving the majority of the soot on the skin. In either case, the overall pattern of soot distribution and its area should be documented. Keep in mind that some modern ammunition is quite "clean," with much less soot and powder deposition than might be expected.

Loose contact wound with a flare of loosely adhere Loose contact wound with a flare of loosely adherent soot on the surrounding skin.

Bullet wipe

Take care not confuse soot surrounding a close (contact or intermediate) range firearm wound with bullet wipe. As a bullet passes though the barrel of a firearm, it picks up a coating of powder, soot, lead, dirt, oil, or any other material soiling the bore of the gun. This may be transferred to or "wiped" on the edges of the bullet defect on the skin or clothing of the victim, presenting as a gray, thin rim of discoloration at the margin of the wound (see the image below). It may be seen with either close range or distant wounds and is not related to range of fire.

Bullet wipe on clothing overlying a gunshot wound. Bullet wipe on clothing overlying a gunshot wound.

Intermediate range wounds and gunpowder stippling/tattooing

As a muzzle is moved farther away from the victim's skin, beyond contact or loose contact range, the phenomenon of gunpowder stippling, also commonly known as powder tattooing, may occur. This is caused by the impact of partially burned or unburned gunpowder particles on the victim's skin, causing tiny abrasions. The presence of stippling/tattooing indicates and defines an intermediate range wound. In some cases, the particles of powder may be embedded in the abrasions. Such areas may be examined under magnification to determine the shape and size of marks, as well as the presence or absence of powder grains.

Because various types of gunpowder have different shapes (eg, ball, flattened ball, flake, cylindrical), stipple marks may also have correspondingly different shapes. In the case of handguns, stippling/tattooing is typically seen with a muzzle-to-target distance range from about 1 cm to 1 m or less. By measuring the dimensions of the area of stippling on a victim's skin and comparing it with that found on test firing a suspect weapon at varying known ranges, an estimation of muzzle-to-target distance may be determined.

When measuring the extent of stippling, one should measure the diameter of the primary mass of stipple marks, without including the occasional outlier. The distribution of the stippling around the wound should also be noted (for example, equal over all quadrants surrounding the wound vs more prominent over some quadrants). See the following image.

Stippling (tattooing) surrounding gunshot wound. Stippling (tattooing) surrounding gunshot wound.

If a firearm muzzle is close enough to the victim, both soot deposition and stippling may occur, as shown in the image below. This generally indicates a narrow range of fire, with a muzzle-to-target distance of a few centimeters.

Stippling and soot deposition surrounding a gunsho Stippling and soot deposition surrounding a gunshot wound.

Many phenomena may mimic true stippling or powder tattooing (pseudostippling). Impact abrasions with dirt or gravel, insect feeding marks, bullet splatter (caused by a bullet impacting a hard surface near the body and extensively fragmenting), needle suture marks, and tiny abrasions caused by postmortem shaving are but a few things that may cause confusion. However, true gunpowder stippling marks are usually fairly similar in size and shape as well as evenly distributed. Pseudostippling marks are often quite variable in size and configuration. See the following image.

Punctate impact abrasions from a fall onto a grave Punctate impact abrasions from a fall onto a gravel surface, mimicking gunpowder stippling.

If the muzzle of a gun is held close to the skin, at an acute angle to the body, an angled firearm entrance wound may result. In such cases, the deposition of soot and/or powder stippling at different points around the wound will vary asymmetrically according to the angle of the trajectory and the muzzle-to-target distance. Space does not allow for description of the many variants of this type of wound here, so readers are referred to the excellent discussion of this topic in DiMaio's textbook. [2] However, the zones of soot deposition or powder stippling will generally be denser on the side of the wound adjacent to the muzzle, but they will be broader and less dense opposite the muzzle of the firearm (see the image below).

Asymmetric zone of stippling surrounding a gunshot Asymmetric zone of stippling surrounding a gunshot wound, indicating an angled, intermediate gunshot wound. Faint soot is also evident on the lower border of the wound, opposite the zone of stippling. The muzzle of the firearm was below and to the right of the wound.

Clothing or other coverings may partially or completely screen out soot or gunpowder stippling from the body. Therefore, clothing overlying a firearm wound should always be evaluated directly by the forensic pathologist and submitted to more extensive criminalistic testing for firearm residues if range of fire is a critical issue.

Graze wounds

The trajectory of a projectile may be tangential to the skin surface. In such a case, a bullet may skim across the skin, disrupting the superficial layers of the skin and subcutis, producing a graze type wound of the skin. It is often difficult to determine the directionality of a graze wound, but occasionally a well-formed abrasion will be present at one end of the graze wound, indicating the site of initial contact by the bullet. Sometimes, the tearing of the skin by passage of the bullet results in skin tags that protrude into the wound. Generally, these tags will point toward the direction from whence the bullet came. If this finding is present and consistent, an opinion regarding the path of a bullet may be formed. See the following images.

Graze wound due to buckshot pellet. Note the abras Graze wound due to buckshot pellet. Note the abrasion at the left edge of the wound and the skin tags pointing leftward into the wound. The pellet track was left to right.
Graze wound of the head with identifiable tiny ski Graze wound of the head with identifiable tiny skin tags (pointing left) and an abrasion at the left end of the wound. The bullet traveled left to right.
Tangential, superficial, perforating gunshot wound Tangential, superficial, perforating gunshot wound. But for the narrow bridge of intact skin in the center of the wound, this would qualify as a "graze" wound.

Atypical entrance wounds, intermediary target effects, re-entrant wounds

The typical round-to-oval shape of a firearm entrance wound results from a stabilized, rapidly rotating bullet impacting and perforating the skin nose first. If the bullet has been deformed or destabilized, an atypical entrance wound may result, as seen in the image below. [11] Such an atypical wound will have an irregular shape with irregular abrasion at the margin.

Atypical gunshot wounds of entrance. Atypical gunshot wounds of entrance.

A bullet may be destabilized by striking a so-called intermediary or interposed target. This may be any structure that the bullet perforates before striking the victim. Automobile doors or glass, house doors or windows, and pillows are common intermediary targets. When this occurs, the bullet may yaw instead of proceeding in a stabilized, nose-forward path. This may cause the bullet to strike the victim sideways or base first. The bullet may also become deformed and misshapen, and it may break up, with fragments of the bullet and/or the intermediary target being driven into the body. The resulting wound(s) is (are) large and irregular, and smaller satellite wounds resulting from impacts by the multiple fragments may also be seen on the surrounding skin. When a bullet ricochets off a hard surface before striking a body, it will likely deform, so a similar atypical wound may be produced. [24] See the following image.

Multiple, irregular wounds due to an intermediary Multiple, irregular wounds due to an intermediary target effect.

A bullet may also pass through one body part, usually an arm or leg, before entering another part of the body, such as the trunk. The wound on the trunk is referred to as a re-entrant or re-entrance wound, and it may be irregular, with characteristics of an atypical firearm wound. If the 2 body parts are in close opposition when the wound is received, both the exit wound and the re-entrant wound may show contusion and/or abrasion. See the images below.

Re-entrant gunshot wound, passing first through th Re-entrant gunshot wound, passing first through the arm and then into the chest. Note the contusion around the exit wound of the arm and the irregular abrasion around the re-entrant wound of the chest.
Close-up photograph of the re-entrant gunshot woun Close-up photograph of the re-entrant gunshot wound in the previous image.

Exit wounds

Exit wounds are usually irregular, have no abrasion rim, and do not display soot deposition or stippling. They may have a stellate configuration, or, particularly in the event of a low-velocity exit wound, have a slitlike configuration. These can be deceptively sharp appearing and can mimic a stab wound. See the following images.

Exit wound. Note the irregularity and lack of an a Exit wound. Note the irregularity and lack of an abrasion rim.
Irregular exit wound. Irregular exit wound.
A slitlike, low-velocity exit wound. A slitlike, low-velocity exit wound.

A common misconception among untrained individuals is that exit wounds are always larger than entrance wounds. However, this is often incorrect, particularly in the case of contact wounds of the head. As noted earlier, such entrance wounds are often large and stellate, whereas the corresponding exit wound may be quite small. The protrusion of fat or viscera through a wound has also been misinterpreted to indicate that the wound is an exit wound. In reality, fat or viscera may herniate from a wound due to the effects of gravity or pressure, and this finding cannot be used to determine entrance versus exit wounds.

A shored exit wound results when the skin at the point of bullet exit is supported or buttressed by some object causing abrasion around the exit wound. [25] The object may be close-fitted or heavy clothing, the floor beneath the victim, a chair back if seated, or any other item that presses against the exit wound area. In such a case, the skin at the exit point is tented outward by the exiting bullet and driven into the supporting or shoring material, causing abrasion, contusion, and/or laceration of the skin around the exit wound. The abrasion may be patterned, recapitulating the shape and character of the overlying "shoring" material. In some such cases, the bullet will fail to exit the skin and will be found in the subcutis or dermis, while causing abrasion or contusion of the overlying skin. See the images below.

Shored exit wound. Note the irregular wound with a Shored exit wound. Note the irregular wound with a well-formed abrasion surround defect.
Exit wound with "shoring." Note the prominent, mar Exit wound with "shoring." Note the prominent, markedly irregular abrasion rim around the irregular wound.
Shored exit wound. Shored abrasion above the wound Shored exit wound. Shored abrasion above the wound perforation recapitulates the shape of an overlying clothing button.

Palmar or plantar wounds

Entrance firearm wounds on the palms or soles are often not typical, being irregular and devoid of abrasion rims (see the following image). Stippling may not be easily seen on wounds of these areas, and marginal tears may also be present at the wound edges. Consequently, determination as to whether a wound of the palm or sole represents an entrance versus an exit wound must often be determined by factors other than wound morphology.

Gunshot entrance wound of the palmar surface of a Gunshot entrance wound of the palmar surface of a thumb.

Beveling

When a bullet strikes a flat bone, such as skull, the phenomenon of beveling may occur. When the bullet perforates the bone, the surface opposite that which is initially struck is fractured away surrounding the bullet perforation. The beveled surface has a cone like shape, with the apex of the cone pointing toward the muzzle of the firearm. Hence, the entrance defect a bullet makes in the skull will have beveling of the inner table of the cranium (internal beveling), as seen in the first image below. The exit defect will display external beveling, as shown in the second image below.

Internal beveling of a contact entrance wound of t Internal beveling of a contact entrance wound of the head. Note the soot on the internal table of the skull.
View of the internal table of the skull with an ex View of the internal table of the skull with an exit gunshot defect. No internal beveling is present. External beveling of the outer table would be expected in this type of defect.

Such beveling may be very helpful in determining the path of a bullet if the wounds of the skin are indeterminate, altered or absent (in decomposed or skeletonized bodies, for example). Although beveling is most commonly encountered in the skull, it may also be quite helpful when involving the ribs or other flat bones. Even if beveling is not present, extrusion of splinters of bone along the wound path may also occur and is indicative of the path of bullet travel.

Keyhole wounds

Keyhole wounds occur when a bullet strikes the skull tangentially, causing a single, elongated defect that demonstrates characteristics of both an entrance wound (internal beveling) at the point the bullet initially strikes the skull and characteristics of an exit wound (external beveling) distal to this. [26] This results in a defect reminiscent of an old skeleton keyhole. The bullet may completely exit the skull through the keyhole defect, it may enter the skull, or it may fragment, with a portion remaining in the skull while another portion exits. The direction of travel is easily discerned from a well-formed keyhole defect, because it proceeds from the internally beveled end toward the externally beveled terminus. See the following image.

Keyhole wound of a skull's outer table. The bullet Keyhole wound of a skull's outer table. The bullet passed from left to right in this photograph.

Intraoral wounds

Intraoral firearm wounds are commonly seen with self-inflicted (suicidal) firearm wounds. Like other types of firearm wounds, they may demonstrate soot or stippling on the mucosa of the palate or pharynx (see the image below). Stretch lacerations of the lips may occur with intraoral firearm wounds if the ammunition is sufficiently powerful, a result of the rapid and forceful expansion of gas issuing into the oral cavity. Extensive facial fracturing may also result.

Suicidal gunshot wound on the palate of the oropha Suicidal gunshot wound on the palate of the oropharynx.

Blood spatter and soot deposition

Contact firearm wounds typically cause spattered blood to be deposited on the firearm and, often, the hand or body of the shooter, as seen in the following image. Such spatter may take place in other than contact wounds, with its degree decreasing with the muzzle to target distance.

Blood spatter and soot deposited on a hand that gr Blood spatter and soot deposited on a hand that gripped the barrel of a firearm during a suicidal gunshot wound.

Soot may also be deposited on the hands of a shooter or a victim at close range. This soot may issue from the muzzle of the firearm, or from the cylinder gap of a revolver. In self-inflicted wounds, the grip of a firearm is often held with one hand, while the opposite hand grips the barrel of the weapon near the muzzle to steady it against the body. In such a case, it is common for soot from the muzzle to be deposited on the dorsal web of the thumb and the adjacent lateral aspect of the index finger of the steadying (non-firing) hand. Other residues such as rust may be left on a hand in prolonged contact with a metal firearm, and occasionally, an imprint of a handgun grip may be left on the palm of a hand in which a gun is held. See the images below.

Soot on the palmar surface of a hand, likely from Soot on the palmar surface of a hand, likely from a revolver cylinder gap in a case of suicide by gunshot wound. However, a similar finding could also occur on the hand of a homicidal gunshot wound victim.
Rust on a hand from prolonged postmortem contact w Rust on a hand from prolonged postmortem contact with a gun barrel.

Because hot gases and residues may issue forcibly from the cylinder gap of a discharging revolver, telltale findings may accompany the improper firing of such a weapon. In a self-inflicted firearm wound from a revolver, in which the firearm is held backward and gripped by 2 hands, gunpowder stippling may be found on the ventral forearms due to powder grains issuing from the cylinder gap. If one hand is held over the cylinder area of a powerful revolver, such as a .357 or .44 magnum, the blast from the cylinder gap may be forceful enough to cause significant laceration of the overlying hand, as depicted in the following image.

Laceration of a palm placed over the cylinder gap Laceration of a palm placed over the cylinder gap of a revolver during a suicidal gunshot.

Having discussed some of the basic principles of firearm wounds due to handguns, we will now turn to some unique features of wounds from other types of firearms, such as shotgun and rifle wounds.

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Shotgun Wounds

Shotgun wounds are unique by virtue of the fact that the ammunition (referred to as a shotshell) usually contains multiple, small projectiles (shot) instead of a single bullet. However, in a contact shotgun wound, the shot charge enters the body en masse, causing a wound that resembles one due to a single projectile. In such a case, there may be a round-to-oval wound with marginal abrasion. Due to the long barrels typical of shotguns, combustion of the powder charge may be more complete, such that soot and powder stippling may be less apparent than in wounds seen with handguns.

Once a shotshell has been fired, the mass of pellets gradually begins to expand and separate as distance from the muzzle increases, and this allows assessment of range of fire in most shotgun wounds.

As the muzzle-to-target distance increases from a contact wound, a more irregular entrance wound with scalloped edges may occur due to early pellet spread. As distance increases to a few meters, the margin of the wound will become ragged, and at a slightly longer distance, discrete individual "satellite" defects may be seen around the main wound due to individual pellet strikes. See the following images.

Close-range shotgun wound. This photograph shows a Close-range shotgun wound. This photograph shows a single defect with ragged, scalloped edges and a few satellite defects.
Slightly more distant shotgun wound. This photogra Slightly more distant shotgun wound. This photograph shows a large, dominant, central defect with smaller satellite defects surrounding it.

Beyond this point, as range increases, the main perforation becomes progressively less defined and individual pellet defects are more widely distributed. The precise rate of this pellet spread is highly variable, depending on such factors as type of firearm, shell construction, and choke (muzzle constriction) of the shotgun. When determining range of fire by the degree of pellet spread, only a very rough approximation may be made, unless the actual firearm and ammunition are available for test firing.

Stippling may also occur around shotgun wounds. The stippling may be due to powder particles as in handgun wounds, but a similar phenomenon may be seen in shotgun wounds inflicted by buckshot rounds. Buckshot shells may contain a granulated plastic buffer admixed with the shot pellets to cushion them when the round discharges. Upon firing, the granules of filler may produce stippling of the skin at a greater range (up to 3 m) than powder particles, as seen in the image below.

Shotgun wound due to buckshot (tangential), with s Shotgun wound due to buckshot (tangential), with stippling due to granulated plastic buffer/filler.

At distant ranges, pellet spread may be such that no main pellet mass perforation is present, and the individual pellet wounds appear evenly distributed, as depicted in the following image.

Distant shotgun wound with multiple, evenly distri Distant shotgun wound with multiple, evenly distributed discrete defects due to birdshot.

Most modern shotgun shells have the projectiles (shot) contained in a plastic cup, with slit sides forming petals that allow the cup to open as it leaves the barrel. On exiting the muzzle, the cup is intact, and it contains the shot as a single mass. Due to aerodynamic pressure, the petals of the cup rapidly begin to open and extend once it has left the muzzle, and after a few feet, are completely folded back. At short ranges, the skin around the wound may be marked or abraded by the extended petals of the cup, which can be seen in the image below.

Mark due to symmetrically extended petals of a sho Mark due to symmetrically extended petals of a shot cup.

At slightly longer distances, the completely folded petals may not mark the skin as the shot charge and cup enter the skin together through a single defect. At still longer distances, the cup will fall away from the shot charge and may abrade the skin separately at some distance from the main shot mass. At distances beyond about 20 feet, no marking of the skin by the shot cup will usually be seen. Most modern shot cups have 4 petals when fully extended, although the smallest shotshell, the .410, usually has only 3 petals.

Target shotshells, buckshot rounds, or older ammunition may contain no shot cup. Instead, a series of cardboard, plastic, or felt discs (wadding) may be placed over the powder charge, beneath the pellets. These may also mark the skin at close ranges (see the following image).

Irregular wadding mark (abrasion) at the periphery Irregular wadding mark (abrasion) at the periphery of a close-range shotgun wound.

In any case, all wadding or shot cups should be recovered from the body during autopsy examination, as their characteristics may provide insight into the type of ammunition used. Their presence within the body also has bearing on the range of fire. As wadding or shot cups are difficult or impossible to visualize on radiographs, a careful manual and visual search of the wound track is indicated to find them in appropriate cases.

Another projectile that may be fired in a shotgun is the slug. This consists of a single, large-bore projectile, usually lead. The most common type of slug is the Foster slug, composed of lead with a hollow base and diagonal "vanes" milled or cut into its surface to stabilize the projectile. The Foster slug produces a large entrance wound and does not usually exit the body; it does often, however, fragment into a few large pieces. Some other types of slugs are less common in the United States, including sabot and Brenneke rounds. The sabot round has a projectile smaller than the shotgun bore diameter, enclosed in a plastic casing or "sabot" that falls away as the unit exits the muzzle of the gun. At close ranges, this sabot may mark the skin around the wound. The Brenneke round consists of a lead projectile with a wad that is actually screwed to its base; as such, this round has a fairly distinct appearance on radiographs.

Contact and intraoral shotgun wounds of the head may cause explosive damage of the skull, rendering the identification of entrance and exit points difficult. However, reapproximation of wound edges and bones will often show areas of skin abrasion or soot deposition to indicate the site of the entrance wound. Gray lead markings on the skull caused by shot pellet strikes may be seen, assisting in the determination of trajectory of the shotgun blast. See the image below.

Impact sites of lead pellets on the inner table of Impact sites of lead pellets on the inner table of a skull due to a shotgun wound of head.
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Centerfire Rifle Wounds

Wounds from centerfire rifles differ from those made by handguns, primarily because of the much higher velocity and kinetic energy of the projectiles. Recall that the kinetic energy (E) of a projectile increases as the mass (M) and especially the velocity (V) increase, according to the formula E = MV2. Rifle entrance wounds are typically regular and sharply punched-out if no intermediary target or other destabilizing influence is applied to the bullet. Abrasion rims may be thin to absent, and there may be tiny radial "microtears" at the margin of the wound. Wounds due to 5.56 X 45 mm cartridges will sometimes have a hexagonal abrasion rim (see the image below).

Distant entrance wound due to high-velocity rifle. Distant entrance wound due to high-velocity rifle. Note the absence of residues surrounding the wound and the presence of hexagonal abrasion rim.

Because of the high velocity associated with centerfire rifle wounds, bullets often fragment extensively within the body, resulting in a so-called "lead snowstorm" appearance on radiographs. As the muzzle-to-target distance increases, bullet velocity and energy will decrease and so will fragmentation. Although it will usually be less extensive in long-distance wounds, significant bullet break-up is still the rule, unless the bullet is heavily constructed. See the following images.

Radiograph of a high-velocity rifle wound. Note th Radiograph of a high-velocity rifle wound. Note the extensive fragmentation of the projectile.
Radiograph of a high-velocity rifle wound showing Radiograph of a high-velocity rifle wound showing the typical "lead snowstorm" pattern of bullet disintegration.

When a bullet passes through tissue, it crushes tissue, resulting in a permanent cavity. It also causes a short-lived temporary cavity, the size and shape of which is greatly influenced by the velocity of the bullet. Because this cavity is partially dependent on velocity, it is much more prominent in centerfire rifle wounds than those due to handguns. The deformation of tissue due to this cavity may cause significant stretching and tearing of the skin and soft tissues of the injured area, the severity of which is partially determined by the elasticity and resilience of the injured organs (see the images below). If a bone is struck and fragmented, the tissue damage will be amplified by bone fragments driven peripherally by the bullet.

Entrance wound due to a high-velocity rifle. Due t Entrance wound due to a high-velocity rifle. Due to temporary cavity formation and resultant laceration of skin, the actual site of the entrance is difficult to see (semi-circular partial defect at the left of lower margin of wound).
Exit wound from a high-velocity rifle injury. Exit wound from a high-velocity rifle injury.

Contact rifle wounds show characteristics similar to handgun wounds, although like shotgun wounds or very powerful handgun wounds, they may have explosive effects when applied to the head. Similar to that of long-barreled shotguns, soot and stippling may be less prominent than that seen in short-barreled handguns. Even distant wounds of the head due to high-velocity rifles may be deceptively stellate because of temporary cavitation.

Projectiles commonly perforate (pass through) one area of the body, such as an arm or leg, before striking the head or torso. In such cases, the initial extremity wound causes destabilization of the bullet, often resulting in a large, atypical re-entry wound on the head or torso (see the following image). If the extremity is in contact with or closely approximated to the torso, there may be contusion and/or abrasion of the skin around the exit and re-entrant wounds.

Re-entrant gunshot wound, passing first through th Re-entrant gunshot wound, passing first through the arm and then into the chest. Note the contusion around the exit wound of the arm and the irregular abrasion around the re-entrant wound of the chest.
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Self-Inflicted (Suicidal) Firearm Wounds

A few comments are in order regarding self-inflicted firearm wounds.

Like firearm wounds in general, some myths regarding suicidal wounds persist. Handguns are the preferred method for suicide in many areas, and the demographics of such wounds indicate that they will be seen in all racial and ethnic groups as well as both sexes. A wide age range is also represented in adults.

Suicide notes are found in a minority of suicidal deaths due to firearm wounds, just as in general. The wounds are most common on the head, [27] but in a significant number of cases, they are on the side of the head opposite that of the dominant hand. Because of this, "handedness" is not of much use in determining if a wound was self-inflicted or not. Most are intraoral (see the image below) or on the temporoparietal regions, but finding wounds on the posterior reaches of the head or neck is not particularly uncommon.

Suicidal gunshot wound on the palate of the oropha Suicidal gunshot wound on the palate of the oropharynx.

The demographics, location, and characteristics of a wound may give some indication of the statistical likelihood of the suicidal nature of the injury, and many authors have addressed this issue. [28, 29, 30] Such information, however, does not provide definitive indication or refutation of a suicidal manner of death.

Suicidal wounds will be either contact or intermediate range morphologically, unless an intermediary structure such as a pillow has been interposed between the body and the muzzle of the weapon. However, some rather ingenious devices have been rigged by individuals intent on taking their own life while attempting to camouflage the event as a homicide. A thorough scene investigation is imperative, as it is rare for examination of the body alone to indicate that a firearm wound is suicidal. As in so many types of cases examined by the forensic pathologist, the autopsy on its own does not give the manner of death in suicidal firearm wounds but merely supports the information found during the remainder of the investigation.

It is also important to document the location of a firearm relative to the body in a putative suicidal firearm wound case. Although a dropped weapon may be found up to a few feet from the body, [31] finding a firearm a significant distance away from the subject of an incapacitating wound would cause one to reconsider the possibility of a suicide. In the case of a wound that would not be immediately incapacitating, however, the firearm might be found a considerable distance from the point of death, as the victim may have walked some distance after sustaining the wound.

Along the same lines, multiple firearm wound suicides are not uncommon. [32] In some cases, an initial firearm wound may not prove fatal. This is seen sometimes when a handgun is placed beneath the chin but the head is tilted too far backward, resulting in a wound track through the floor of the mouth, maxilla, and nasal region. Although serious and potentially fatal, this type of wound might not immediately kill or incapacitate, causing the subject to fire a second round with greater effect. Wounds to the trunk are often not immediately incapacitating, allowing ample time for the decedent to fire multiple times.

In the case of long-barrelled weapons, consideration must be give to the location of the wound and whether it would have been possible for the decedent to position the weapon and manipulate the trigger of the firearm to inflict the wound. Remember that feet and toes, sticks, strings, or other devices may called into play to activate a trigger, so the scene must be thoroughly examined.

Finally, there is great variability in the classification of self-inflicted firearm wounds as "suicide" among forensic pathologists. Some consider that intent to die is required to classify a death as a suicide. Others counter that proof of intent to die is not required to yield a suicidal manner of death. A prime example is a death due to "Russian roulette." Many consider such deaths to be suicidal, whereas others consider them to be impulsive acts, often facilitated by ethanol or other intoxicants, and not indicative of a self-destructive intent.

Similar quandaries arise in cases when a firearm that is "thought" to be unloaded is placed against the head and fired, resulting in the death of the shooter. In cases of deaths caused by another person, a similar quandary exists. When a person is inadvertently killed by a hunter who mistakes him for a game animal and fires, is it a homicide or an accident? Although the hunter may not have intended to kill the victim, he did willfully discharge the firearm at the target, albeit erroneously.

These inconsistencies indicate a general lack of agreement on the definitions of various manners of death among forensic pathologists and variation in the philosophic approaches to manner of death determination. In any case, most forensic pathologists will agree that truly accidental firearm wounds are rare.

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Common Misconceptions

Misconceptions among lay people and physicians abound regarding firearm wounds. [33] For example, many physicians appear to believe that entrance firearm wounds are always smaller than exit wounds. This frequently causes confusion in cases of contact wounds of the head, which, as noted earlier, are often large and stellate (see the following image). It is not uncommon for clinicians such as emergency department physicians or trauma surgeons to misinterpret the directionality of perforating wounds [34] ; therefore, it is generally preferable for such specialists to defer such interpretation to the forensic pathologist, at least in fatal cases.

Stellate hard contact wound of the head. Note the Stellate hard contact wound of the head. Note the abundant soot in the wound depths.

Thanks to Hollywood portrayals of gunfights and firearm wounds, many people are of the erroneous opinion that a single firearm wound will cause immediate incapacitation in all cases and that a bullet will knock a victim to the ground, against a wall, or through a window. None of this, of course, is true.

Victims often sustain firearm wounds, sometimes multiple wounds, without becoming incapacitated. [35] Only a significant central nervous system injury or a wound that compromises the stability and integrity of the supporting skeleton can generally be expected to cause a victim to stop and fall to the ground immediately. The kinetic energy of a bullet striking a target may appear fairly high (in the range of 500-1000 ft-lb of energy for a typical handgun cartridge), but because the bullet mass is so small, the actual momentum transferred to the target is quite small. As such, bullets do not throw or knock victims about.

Conversely, typical media presentations show firearm victims being rather innocuously wounded in locations such as the extremities or shoulder by a well-placed shot from a hero who "only wanted to 'wing' him, not kill him." In fact, wounds of the extremities are often fatal and/or maiming injuries, and in a gunfight, such precise shot placement on a moving target is highly improbable.

Although the effects of firearm wounds are often understood incorrectly, other facets of the subject are also improperly understood or reported by lay persons, medical personnel, or the media. Nowhere is this more evident than in discussions of the alleged use of "assault rifles" by criminal elements in the United States. In truth, assault rifles are fully automatic weapons that are quite difficult for civilians to obtain, and their criminal use is seen very rarely in most jurisdictions, if at all. Semiautomatic rifles that are commonly used by civilians (both the law-abiding and criminal element) are not fully automatic in their function and thus have little in common with true assault rifles, other than their appearance. Such weapons are also actually not particularly powerful when compared with typical hunting rifles.

The physician is well advised to view all statements about firearms from media or other similar sources with some suspicion until they are corroborated by an expert in the field.

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Issues Arising in Court

The imagination of trial attorneys when questioning an expert witness will often amaze even experienced forensic pathologists, thus, the range of issues that the physician will be expected to address in court is practically infinite. However, certain questions arise in a high percentage of firearm wound cases and are briefly discussed below.

The pathologist is expected to give the cause of death in the case. Although this may seem obvious, remember that in a court of law, until evidence is actually given in the courtroom, it cannot be considered by the jury. Thus, testimony on such apparently obvious information will usually be required. Sometimes, little more will be asked of the forensic pathologist. If there are multiple wounds, he or she may be asked which wounds were fatal and which were survivable. In responding, the witness should remember that forensic pathologists often have a skewed view of survivability, as their "patient" population is composed exclusively of nonsurvivors. In some cases, it may be prudent to defer such judgments to practitioners of other specialties, such as trauma surgeons. If one chooses to address such a question when asked, keep in mind that some victims can and do survive even devastating injuries, whereas others die from wounds that would often be survivable.

Range of fire is often questioned, particularly if one side of the dispute alleges that a struggle took place at close range at the time of the shooting. Characteristics of the firearm wound may assist in this determination, but the presence of overlying clothing must be considered. If present, the clothing should be examined in a crime laboratory to properly assess the degree of soot and/or powder deposition present. Only a gross estimate of range of fire may be given (for instance, "inches," "up to a few feet," "more than a few feet") unless the firearm and ammunition used in the shooting have been recovered and test fired for a more accurate range of fire determination.

Incapacitation due to a firearm wounds will often come into question. As noted elsewhere in this article, only wounds that significantly injure the upper central nervous system can be reasonably expected to cause immediate incapacitation, whereas those that cause significant fractures of the supporting skeletal elements may have deleterious effects on movement of the victim. Even victims with devastating injuries may continue to function for a period, and this may involve fleeing, continuing an assault, running, or other activities. The period in which this may occur is highly variable according to the degree of injury and personal factors that are difficult to quantitate.

One of the more common queries in court relates to the trajectory of the bullet striking a victim. The forensic pathologist determines an approximate path of the bullet through the body (based on the standard anatomic position) but not through space. As the human body can move and assume an infinite variety of positions, the actual trajectory of the bullet through space will be dependent on the position of the body when the wound is inflicted. This is rarely known, but it is common for opposing attorneys to offer hypothetical scenarios on the position of a body, asking the pathologist if these scenarios are consistent with the wounds found.

The question is perfectly legitimate, and it should be answered honestly to the effect that the postulated position is "consistent" but is not the only possible position. Unfortunately, the multitude of possibilities in such cases provide sample opportunities for opposing attorneys to attempt to gain ground in the courtroom, so prolonged questioning about positioning and bullet paths can be expected in some cases.

The pathologist is sometimes asked to identify a bullet removed at autopsy in court. Because it is practically impossible to visually identify a bullet that was likely removed years earlier, the best response is that the bullet can be identified by the labeling on the container in which it was placed, that having been handled with a strict chain of custody throughout its examination. It is up to the prosecuting attorney to demonstrate that the chain of custody was maintained. Opening containers and removing bullets and other evidence for examination in court is generally poor practice, although it is often requested that the witness do so as part of the "theater" of the courtroom. If told to do so, there is no recourse, except to request a pair of gloves with which to handle the contaminated evidence.

The forensic pathologist must attempt to answer all questions accurately and honestly, even if it is difficult to determine why the question is being asked. If the question is confusing or difficult to understand, the pathologist should not hesitate to say so and to ask for clarification. If the answer requires explanation or expository statements, the pathologist should attempt to give them, and if there is objection, he/she should simply state that the question cannot be answered without explanation. Most judges will allow an expert witness to explain an answer rather than being confined to a simple "yes/no" choice of answers. If the answer to a question is not known, the pathologist should simply say so. It is a truism in forensic pathology that the willingness to say "I do not know" is a measure of the maturity and experience of the practitioner.

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Additional Resources

The references below are resources for more detailed information regarding firearms and firearm injuries:

  • DiMaio VJM. Gunshot Wounds: Practical Aspects of Firearms, Ballistics, and Forensic Techniques. 2nd ed. Boca Raton, Fla: CRC Press, 1999.
  • Bussard ME, Wormley SL Jr, Zent J, eds. NRA Firearms Sourcebook. Washington, DC: The National Rifle Association of America, 2006.
  • Spitz WU. Injury by gunfire. In: Spitz WU, ed. Medicolegal Investigation of Death. 4th ed. Springfield, Ill: Charles C Thomas, 2006: 607-746.
  • LaGarde LA. Gunshot Injuries. 2nd ed. New York, NY: William Wood & Co; 1916.
  • Frost RE, Sligh TS. A review of firearms terminology for the forensic pathologist. Academic Forensic Pathology, 2013: 3(2):116-138.
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