Forensic Autopsy of Sharp Force Injuries

Updated: Oct 18, 2016
  • Author: Joseph A Prahlow, MD; Chief Editor: J Scott Denton, MD  more...
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Overview

Overview

Injuries produced by pointed objects or objects with sharp edges are referred to as "sharp force injuries." Sharp force injuries are characterized by a relatively well-defined traumatic separation of tissues, occurring when a sharp-edged or pointed object comes into contact with the skin and underlying tissues. Three specific subtypes of sharp force injuries exist, as follows: stab wounds, incised wounds, and chop wounds.

History

Along with other primitive injury types, such as blunt force trauma, drowning, thermal injury, and other environmentally induced forms of injury, sharp force injuries have been around for a long time. Numerous accounts of deaths due to sharp force trauma are documented in the Old Testament of the Bible, as follows:

"When Phinehas…saw this, he left the assembly, took a spear in his hand and followed the Israelite into the tent. He drove the spear through both of them -- through the Israelite and into the woman's body." Numbers 25:7-8

"But Jael, Heber's wife, picked up a tent peg and a hammer and went quietly to him while he lay fast asleep, exhausted. She drove the peg through his temple into the ground, and he died." Judges 4:21

Even with the advent of more modern injury types, such as gunshot wounds, motor vehicle collisions, medical therapy-related incidents, and injury related to alternating current electricity, sharp force injuries have remained relatively common within the world of death investigation. In fact, as society has become more modern, a variety of new, more "advanced" sharp force injury types have emerged. In this chapter, we will discuss sharp force injuries and the deaths that result from such injuries.

Epidemiology

Deaths due to sharp force injuries are less common than those due to blunt trauma, gunshot wounds, asphyxial mechanisms, and drug toxicity. The frequency of such deaths varies from one jurisdiction to another. The most common manner of death associated with sharp force trauma is homicide, followed by suicide. Accidental sharp force injury fatalities do occur but are relatively rare. [1]

A study performed at an urban medical trauma center evaluated the trauma deaths that passed through the emergency department during an 11-year period from 1994 to 2005. Sharp force (stab wounds) accounted for 11% of the cases, compared with gunshot wounds (56%), falls (11%), motor vehicle collisions (9%), assaults (7%), and struck pedestrians (4%). [2]

A report by the Center for Disease Control evaluated violent deaths occurring in 16 states during the year 2006. In the report, a "violent death" is defined as a death resulting from the intentional use of physical force or power against oneself, another person, or a group or community. [3] Sharp force injuries accounted for 1.7% of all suicides, compared with the top 3 means of suicide: firearms (51.3%), hanging/strangulation/suffocation (22.1%), and poisoning (18.4%). Sharp force injuries accounted for 12.1% of all homicides compared with 65.8% for firearms and 4.6% for blunt trauma. [3]

Overview of the entity

As mentioned above, the term "sharp force injury" encompasses essentially 3 separate but related injury types. Stab or puncture wounds are produced by sharp, pointed objects, wherein the direction of force is more perpendicular to the skin surface, as opposed to tangential or parallel. In most instances, the wound is deeper than it is long on the skin surface.

In contrast, incised or cut wounds are produced by sharp-edged objects, wherein the direction of force is more tangential or parallel to the skin surface, as opposed to perpendicular. In most circumstances, the wound is longer on the skin surface than it is deep.

Chop wounds can be considered a combination of sharp and blunt force trauma, wherein a relatively bulky object with an edge, or a fast-moving object with an edge, impacts the body, resulting in injuries that have features of sharp force trauma as well as those of blunt force trauma.

Indications for the procedure

Sharp force injuries fall under the jurisdiction of the medical examiner or coroner. Although not as common as firearms-related injuries, these injuries are often seen in suicides and homicides. Sharp force injuries are also encountered in the setting of multiple injuries related to motor vehicle accidents.

Detailed examination of sharp force injuries, particularly in homicides, can provide useful information regarding the type of weapon that likely inflicted the wounds. This information can potentially guide the police to the recovery of a murder weapon or it can be used to exclude other implements recovered from a crime scene.

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Definitions

It's important for sharp force injuries to be distinguished from lacerations (tearing apart of tissues), which are, by definition, a type of blunt force injury. The presence of "tissue bridging" within the depths of the wound, below the level of the skin surface, represented by nerves, vessels, and other soft tissues that extend across the gap, from one side to the opposite side, are indicative of a laceration, as seen in the image below. Tissue bridging tends not to occur with sharp force injuries, as these structures are typically severed by the sharp/pointed object that results in the separation of the other surrounding tissues.

Laceration (caused by blunt force trauma), mimicki Laceration (caused by blunt force trauma), mimicking a sharp force injury. The presence of "tissue bridging" (arrows) helps to differentiate a laceration from a sharp injury.

A stab wound, or puncture wound, is caused by a pointed object, typically having a sharp tip, when the object is forced into the skin (and underlying tissues) with the direction of the force in a more-or-less perpendicular angle with the skin. Stab wounds are typically deeper (through the skin and into the body) than they are wide (on the skin surface), as shown in the image below.

A stab wound. A stab wound.

The most common weapon used to inflict stab wounds are knives. Examples of other objects that can cause stab wounds include forks, scissors, screwdrivers, arrows, ice picks, and any other cylindrical object that has a sharp or pointed tip.

An incised wound, or cut or "slash," results when an object with a sharp tip or sharp edge, makes contact with the skin (with or without associated underlying tissues), with the direction of the force in relation to the skin occurring in a more-or-less tangential fashion. Incised wounds are typically longer than they are deep, as seen in the image below.

An incised wound of the face. Note that the wound An incised wound of the face. Note that the wound is longer on the skin surface than it is deep.

Examples of objects that can cause incised wounds include knives, razors, box cutters, broken glass, and any other object having a sharp edge or point.

A chop wound is best considered a combined blunt and sharp force injury that is produced by a relatively sharp object wielded with a tremendous amount of force. The object is often heavy and moving at a high rate of speed or with significant angular acceleration. Because of the larger amount of force, chop wounds have features of both sharp and blunt force injuries. As such, chop wounds frequently have marginal abrasions and contusions, and sometimes lacerations, as depicted below.

A chop wound produced by a tomahawklike tool. Note A chop wound produced by a tomahawklike tool. Note the stablike injury as well as the associated marginal abrasions.

Underlying fractures are also common with chop wounds. Examples of objects that can cause chop wounds include crowbars, claw hammers, tomahawks, axes, hatchets, boat propellers, lawnmower blades, and a multitude of industrial and farm machinery.

On the skin surface, the edges of a stab, incised, or chop wound are referred to as the wound's "margins," whereas the ends, or tips, of the wound are referred to as the wound's "angles." The "length" of a wound is measured from one angle to the other. An imaginary line drawn between the 2 angles defines the "long axis" (or "longitudinal axis") of the wound. The "width" of the wound is the widest measurement between the 2 margins, as seen in the images below. The depth of the wound is measured from the skin surface to the deepest point of penetration.

Diagram of sharp force injuries. Upper left: stab Diagram of sharp force injuries. Upper left: stab wounds. Lower left: incised wound. Upper right: chop wound. Lower right: The bracket defines the sharp force wound "margin" or edge, whereas the arrows denote the wound's "angles" or ends. The dashed line shows the "longitudinal axis" of the wound.

If the margins are widely separate from one another in a stab wound, as a result of the elastic forces of the surrounding skin (defined by "Langer's lines" as described in anatomy and surgery textbooks), the wound is said to be "gaping." A nongaping stab wound is sometimes referred to as "slitlike."

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Scene Findings

The scene of death in cases due to sharp force injury are frequently extremely bloody, although this is not always the case. Oftentimes, when skin injuries are gaping open, blood freely flows out of the body, resulting in extensive external blood loss. This may be particularly evident in cases with large, gaping incised wounds. In contrast, in some cases with sharp force injuries, particularly stab wounds, the wound edges remain relatively well approximated, and there is extensive internal bleeding but little external blood.

Blood drip patterns, blood spatter patterns, and footprints, handprints, and fingerprints within blood may all be very important items of evidence at the scene. Photographic documentation and consultation with a blood spatter expert may be in order.

Investigators should attempt to identify the weapon or proposed weapon in all sharp force injury cases. In suicides and accidental sharp force injury deaths, the weapon usually remains at the scene of death. In homicides, the weapon may or may not be present. The weapon may be found at a location away from the body but relatively close by. Occasionally, a perpetrator may have attempted to wash the weapon. In occasional homicidal sharp force injury cases, the weapon breaks off in the body. Body transport personnel, morgue personnel, and pathologists must be aware of this possibility, in order to avoid inadvertent injury. For this same reason, radiographs of injured areas are recommended.

By the very nature of many sharp weapons, most cases of homicidal sharp force injury require close contact between the perpetrator and the victim. As such, important trace evidence (hairs, fibers, fluids) that might potentially link a suspect to the crime might be present on the victim or at the scene. If the attacker sustains injuries during the attack, the suspect's blood and/or hair may also be present at the scene. With certain sharp force homicides, a sexual assault may have preceded or coincided with the sharp force attack. A Wood's light examination of the scene may be helpful in identifying seminal fluid or other trace evidence.

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Trace Evidence

As mentioned above in the scene investigation section, the very nature of many homicidal sharp force injury cases usually requires close contact between the perpetrator and the victim. As such, pathologists and investigators must carefully look for, identify, document, and collect various items of trace evidence on the victim's body and clothing. Items such as hairs, fibers, and various fluids (blood, semen) may be present. A Wood's lamp or other alternate light source can be useful identifying some of these items.

Consideration should be made regarding the collection of a sexual activity kit in any case in which the clothing of the victim is torn, cut, or otherwise removed in such a way to suggest that forced sexual activity might have occurred. In some cases, the victim's genital region is not exposed; however, investigators should still consider collecting evidence, especially from the victim's oral region.

The clothing of a victim of sharp force injury death represents another important component of evidence. Depending on the clothing material type, stab and cut marks within the material may help investigators learn something about the characteristics of the weapon utilized.

The clothing of a victim of sharp force injury sho The clothing of a victim of sharp force injury should be carefully examined, especially for trace evidence and to correlate clothing defects to skin wounds. Occasionally, depending on the type of material, clothing examination can help to determine the type of weapon used.

Occasionally, but not always, suicide victims will move the clothing before injuring themselves. For example, a person may open their shirt before stabbing themselves in the heart. In contrast, it is unlikely that the clothing will be purposefully removed before injury infliction in most homicides or accidents. An exception involves certain homicide cases, in which the perpetrator purposefully moves or removes the clothing as part of a sexual attack or in order to antagonize the victim.

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Gross Examination and Findings

External examination, initial steps

When performing an autopsy on a victim with sharp force injuries, it is sometimes beneficial to photographically document the body as it is first seen in the autopsy room. Some pathologists refer to such photographs as "as is" photographs. Especially in homicide victims, careful evaluation for trace evidence should take place before the body is disturbed. If a sexual activity kit is required, it should be done at this time. X-rays should be taken of all areas where sharp force injuries exist to identify the presence of retained weapons or portions of weapons. A chest x-ray may also be performed at this time to evaluate for possible air embolism. The clothing should then be carefully removed, examined, and retained.

External examination, documenting injuries

After collecting appropriate trace evidence, taking x-rays, and removing clothing, the body should be washed, so that documentation of injuries and photography can take place. Sharp force injuries should be classified as stab wounds, incised wounds, or chop wounds. The margins of a sharp force injury, whether they are stab wounds or incised wounds, are usually "continuous," but they may occasionally have an irregularity along the margin and consequently be described as "discontinuous." In addition, the margins are frequently considered "clean" or "sharp," meaning there are no associated abrasions or contusions.

Occasionally, abrasions and/or contusions occur adjacent to sharp force injuries. These may result from a variety of objects, including the handle of the weapon, such as a knife. When such injuries occur in stab wounds wherein the blade's entire length enters the body, the abrasions/contusions may be considered "hilt mark" injuries. Their presence, along with an accurate measurement of the depth of the wound during internal examination, can help the pathologist to estimate the length of the blade.

Regarding the angles (ends) of sharp force injuries, the angles may be "sharp" (coming to a point), "blunt" (having a squared-off appearance), or "indeterminate" (when a definitive ruling between sharp and blunt cannot be made). It may be useful in some cases to trace the wound margins with a pen after placing clear plastic over the wound.

A stab wound. Note that the left angle has a squar A stab wound. Note that the left angle has a squared-off appearance and is therefore described as being "blunt," whereas the right angle comes to a point and is therefore described as being "sharp."

The location of each sharp force injury should be noted as to its specific body location, with measurement of the distance from the bottom of the foot or the top of the head, the distance from the midline or mid axillary line, and the proximity to a local landmark, such as the umbilicus, nipple, or ear, if such a landmark is nearby. The overall wound length, width, and directionality should be described, as should the appearance of the wound's margins and angles. In some cases of multiple stab wounds, it may be appropriate to group the wounds in the autopsy report provided that measurements of each individual wound have been taken and can be recovered if needed.

An example of a gaping stab wound with associated An example of a gaping stab wound with associated abrasions near the upper left angle. The presence of associated abrasions and/or contusions may result from the "hilt" or handle of a knife or other weapon. Note that the each angle of the wound is sharp.

The directionality of the "long axis" of a sharp force wound can be described as "vertical," "horizontal," or angled, with a general or specific measurement of the angulation. One method is to describe the directionality based on a clock-face configuration. For example, "the long axis of the wound runs between the 1 and 7 o'clock positions." It should be noted that, when using this method in describing incised wounds, it is not meant to imply that the "direction" of the cutting occurred from upper (1 o'clock) to lower (7 o'clock) (see more below as well as in Common Misconceptions).

Nonlinear or irregularly shaped stab or incised wounds can result from irregularly shaped or jagged weapons, from intersecting wounds, or from a twisting weapon/body interaction. The last phenomenon can result in combined stab/incised wounds. It cannot be determined based on the configuration of these wounds whether the assailant twisted the knife while it was in the body or if the victim twisted while impaled, unless there is clear evidence that the wound occurred postmortem.

A stab wound complex that represents 2 intersectin A stab wound complex that represents 2 intersecting stab wounds.

In attempting to determine whether an angle is sharp or blunt, it is sometimes necessary to "reapproximate" the wound margins. In other words, the margins (edges) of the wound can be held together ("reapproximated") in order to better evaluate the angles of the wound, as shown in the photographs below.

A "gaping" stab wound. Note that it is difficult t A "gaping" stab wound. Note that it is difficult to determine if the angles are sharp or blunt.
The same stab wound depicted in the previous image The same stab wound depicted in the previous image, with reapproximated wound margins. Note that reapproximation of the wound edges allows one to determine that the upper angle is blunt, whereas the lower angle is sharp.

Reapproximation of the margins can occur by simply holding the margins together; for photography, some choose to use clear tape over the wound or superglue to bind the subcutaneous tissues together.

Postmortem drying of the wound results in a darkening of the wound, with associated drying and a loss of flexibility. As such, postmortem drying can make evaluation of a wound's margins and angles difficult. Soaking the wounds with a wet towel may facilitate reapproximation of dried wounds.

A stab wound which has become dried out postmortem A stab wound which has become dried out postmortem. Note the dark discoloration of the margins. Even with postmortem drying, it is possible to determine in this case that the left angle is sharp, whereas the right angle is blunt.

The pathway into or through the body should be described. A wound that goes completely through a specific body part is said to have "perforated" that part (see the following 2 images). Conversely, if the wound only goes partly into a body part, it is said to have "penetrated" that part.

A perforating stab wound of the arm. It could not A perforating stab wound of the arm. It could not be determined with certainty which wound represents the entrance and which represents the exit.
The same perforating stab wound as shown in the pr The same perforating stab wound as shown in the previous photograph. After examining and photographing the wounds, a probe can be gently inserted through the wound in order to show that the 2 skin defects connect with each other.

A description of the overall direction of the wound and its maximal depth of penetration should also occur. This is particularly important in deep stab/puncture wounds. It is appropriate to describe the direction within 3 planes, including front/back, right/left, and up/down. Pouring a radio-opaque substance into a stab wound to delineate the wound path is a technique that only works in the world of television fiction.

As in the 2 photos shown above, it is frequently impossible to differentiate entrance stab wounds from exit wounds. It should be noted that extreme care should be employed when inserting probes into wounds, such that no additional tissue damage is produced by the probe. Insertion of probes should only occur after careful examination, documentation, and photography of the "unprobed" wound.

A chop wound represents a combination of sharp and blunt force injuries, typically produced by a heavy or "powerful" object that has an edge that is somewhat sharp to very sharp, or by a sharp object wielded with a tremendous amount of force. The edge of the object creates a sharp force injury, characterized by cutting of the skin and underlying tissues, whereas the intensity of the force, or the relative "bluntness" of the object, results in associated abrasions, lacerations, and/or contusions, with or without underlying fractures. A chop wound's appearance may also aid in determining the type of weapon used, as the wounds may take on the pattern of the weapon.

A chop wound produced by the claw end of a crowbar A chop wound produced by the claw end of a crowbar.

The overall shape of a stab wound tends to mimic the object that caused the wound. As such, wounds caused by knives tend to be linear (or curvilinear). Scissors create a more triangular-shaped stab wound. Objects with a cylindrical shape cause round stab wounds, which may mimic gunshot wounds. Screwdrivers can cause cross-shaped wounds (Phillips head), rectangular wounds (standard head), or even round or square wounds (depending on the shape of the shaft).

Multiple stab wounds produced by a standard screwd Multiple stab wounds produced by a standard screwdriver. Note the rectangular shape of several of the wounds.
Multiple superficial punctures produced by a Phill Multiple superficial punctures produced by a Phillips ("cross-shaped"/"crosshead") screwdriver.

Other sharp objects can produce patterns that correlate with the objects' shapes.

A superficial puncture wound complex produced by a A superficial puncture wound complex produced by a 4-tined dinner fork.
A stab (puncture) wound complex produced by a barb A stab (puncture) wound complex produced by a barbecue fork with 2 tines.

Although the appearance of stab wounds may indicate the shape of the weapon used, such is not necessarily the case with incised wounds; however, occasionally, the appearance of incised wounds may provide some indication as to the weapon type.

Multiple sharp force injuries of the neck produced Multiple sharp force injuries of the neck produced by a broken bottle.

Serrated knives (those having "teeth") frequently produce wounds that are indistinguishable from nonserrated knives; however, if the serrated edge is dragged along the skin surface (usually adjacent to a stab or incised wound), multiple, small, superficial, parallel incised wounds corresponding to the serrated edge's teeth may be evident. Serrations may also be detected on underlying bony structures.

This stab wound of the cheek has a superficial cur This stab wound of the cheek has a superficial curvilinear incised wound that trails away from the posterior margin toward the ear. Note the multiple, parallel, superficial incised wounds extending from the stab wound margins, superior to the longer incised wound. The presence of these marks indicates that the injuries were produced by a weapon with a serrated edge.
A sharp force injury complex of the chest. This wo A sharp force injury complex of the chest. This wound was caused by the serrated-edged blade of a running electric reciprocating saw when the intoxicated operator fell onto the saw. Note the curvilinear to somewhat irregularly-shaped stab wound complex, as well as the marginal abrasions with superficial tooth-mark incisions/abrasions on the left side of the photograph.

When documenting multiple sharp force injuries, it is important to describe every wound. Most pathologists use some type of organizational scheme to keep track of the injuries. For example, some pathologists number the wounds sequentially, beginning from the wound closest to the top of the head and work downward from head to neck to trunk, ending with the arms and legs. Some pathologists describe stab wounds first and then incised wounds. Some combine the methods or use other methods. When there are numerous, similar sharp force injuries within a relatively small surface area, it is appropriate to describe the wounds together as a group or "cluster."

In this case with multiple stab wounds, it would b In this case with multiple stab wounds, it would be acceptable to describe the closely grouped collection of stab wounds within the central chest area as a "cluster," while providing individual descriptions of the wounds of the right side, the right chest, and the left chest near the axilla.
Multiple stab wounds of the back. Many pathologist Multiple stab wounds of the back. Many pathologists would describe these wounds separately; however, some might describe them as a cluster.

"Hesitation marks" are a group of multiple, superficial, roughly parallel, incised wounds, typically present on the palmar (anterior) aspect of the wrists/forearms in suicide victims. [6] The classic case has groups of numerous, bilateral wrist hesitation marks. Hesitation marks may be seen in locations other than the wrists, including the neck, the chest, the antecubital fossa, and the inguinal area. The hesitation marks may be adjacent to a deeper, lethal wound, or they may be totally distant from the lethal wound(s).

Hesitation marks on the wrist of an individual who Hesitation marks on the wrist of an individual who committed suicide via stab wounds of the chest.

Occasionally, no lethal sharp force wound is identified, and autopsy reveals that the cause of death is a suicidal overdose or some other type of traumatic injury. Despite the fact that the presence of hesitation marks is considered by some to be pathognomonic for suicide, it is possible for homicidal sharp force cases to have injuries that are indistinguishable from hesitations marks, although these are less likely to be on the wrists bilaterally. Multiple, superficial, roughly parallel incised wounds on the neck, adjacent to a deep, lethal incised wound, can be seen in victims of homicidal sharp force injury, particularly if torture was employed.

In victims of homicidal sharp force trauma, a frequent finding is the presence of so-called "defensive wounds" or "defense-type wounds." Classic defensive wounds in sharp force injury cases include multiple stab and incised wounds on the upper extremities, typically the fingers, hands, and forearms. These injuries occur as the victim attempts to fend off the attack by raising his or her hands and arms in a defensive posture, and they tend to be more dispersed in their distribution, as compared to hesitation wounds. [6] Similar appearing defensive wounds may occur on the lower extremities when the victim is on his or her back, raising the legs and feet to attempt to block the attack.

Defensive wounds of the hand/fingers. Defensive wounds of the hand/fingers.
Multiple defense-type injuries on the fingers of a Multiple defense-type injuries on the fingers of a homicide victim.
A defensive injury on the hand of a homicide victi A defensive injury on the hand of a homicide victim.

Internal examination

On internal examination, pathologists should describe the pathway of each sharp force injury. In cases of multiple homicidal stab wounds, it is not uncommon for many of the wounds to remain relatively superficial, without penetration of body cavities or internal organs. Occasionally, multiple wound pathways arise from a single skin injury. Presumably in such instances, the weapon simply hit the same location more than once, or the weapon was thrust in and out of the same skin entrance site.

The maximal depth of penetration of each wound should be noted, remembering that, because of the elasticity and flexibility of tissues and organs (and even the rib cage), the depth of penetration does not necessarily mean that a weapon must be that same length. It is entirely possible for a knife with a 3-inch-long blade to produce a wound that is 4 or 5 inches deep. When "hilt mark" injuries surround a stab wound, their presence indicates that the blade was inserted to its maximum possible depth; however, as just stated, because of the elasticity of skin, subcutaneous tissues, and internal tissues, the depth measurement of the wound can still be greater than the blade length. Obviously, it is also possible for a 3-inch-long blade to penetrate less than 3 inches.

The pathway for each wound should be documented, taking note of all organs injured, as well as the direction of the wound. As noted earlier, it is common for many pathologists to provide 3 directions for each wound. For example, a stab wound may have traveled from right to left, upward, and from front to back. Another stab wound might have gone from back to front, slightly downward, without any significant right/left deviation. Other pathologists choose to measure or estimate the angle of each wound, in reference to various anatomic planes.

A stab wound of the inferior vena cava, as well as A stab wound of the inferior vena cava, as well as an associated total transection of the abdominal aorta.

All associated internal injuries should be documented, including accumulations of blood (hemothorax, hemopericardium, hemoperitoneum, retroperitoneal hemorrhage, mediastinal hemorrhage), air embolism, pneumothorax, and evidence of aspirated blood. Radiographs (x-rays) and special dissection techniques may be utilized to identify and document air embolism and/or pneumothoraces. In sex-related homicides, a layered anterior neck dissection should be performed to rule out concurrent strangulation.

Special dissections

When a weapon producing a sharp force injury makes contact with cartilage (or bone), the cartilage (or bone) may sustain injuries that have specific tool-mark impressions that correspond to the weapon. If such markings are unique and detailed enough, tool-mark examiners in the crime laboratory may be able to "match" an injury to a particular weapon. Pathologists should remove the area of cartilage (or bone) containing the tool-mark impressions and retain the tissue in formalin for subsequent analysis.

A sharp force injury of the anterior, cartilaginou A sharp force injury of the anterior, cartilaginous portion of a rib. Examination of the cut surface using a dissecting microscope may reveal tool marks that can be compared to the suspected weapon.

Special dissection techniques used to evaluate for the presence of an air embolism are described in the next section.

Special autopsy procedures

Radiologic examination of the sharp force injury victim is an important part of the forensic evaluation of such cases. Radiologic identification of broken-off portions of weapons, such as knife blades, helps to avoid injury during the autopsy, and subsequent "matching" of the weapon fragments may be possible.

Stab wound with broken-off blade remaining in body Stab wound with broken-off blade remaining in body.
X-ray showing a retained knife blade. X-ray showing a retained knife blade.
Broken-off knife blade removed from a body at auto Broken-off knife blade removed from a body at autopsy.

Chest x-rays performed before autopsy on victims of sharp force trauma may reveal an "air-embolism" within the right side of the heart, seen as a radiolucent (dark) area.

A chest x-ray showing an air embolism within the h A chest x-ray showing an air embolism within the heart. Note the radiolucent (dark) area within the right side of the heart (arrows).

The presence of an air embolism may help to explain why a death might occur relatively rapidly, without extensive external or internal loss of blood. When a relatively large-caliber vein is severed, the continued pumping action of the heart can cause a vacuum-type effect, such that large volumes of air are sucked into the vein. When the air reaches the heart, a "vapor-lock" effect can occur, resulting in cessation of blood flow. This phenomenon can help to explain why, in certain cases, there is not a large amount of blood present externally or internally.

In order to confirm the suspicion of an air embolism within the right side of the heart, pathologists can carefully cut an approximately 4-5-inch × 4-5-inch "window" out of the anterior aspect of the chest wall, overlying the pericardial sac. Some prefer to remove the chest plate in the usual fashion. In either case, care should be taken to avoid disruption of large blood vessels, which can potentially cause air to enter the vessels artifactually.

The heart sac should be opened anteriorly, such that the pericardial cavity can be filled with water, so that the heart is totally submerged. Once submerged, a needle or scalpel blade can be used to puncture the right atrium of the heart. If an air embolism is present, bubbles will escape from within the right atrium. The pathologist can use a water-filled, inverted graduated cylinder to "catch" the air bubbles in order to measure the amount of air trapped within the heart (see the image below).

Checking for an air embolism at autopsy. In this p Checking for an air embolism at autopsy. In this photo, the chest plate was removed very carefully before filling the heart sac with water. An inverted water-filled graduated cylinder is being used to collect and measure the escaping air.

If a pneumothorax is visualized on chest x-ray (a radiolucency), or if one is otherwise suspected at autopsy, the pathologist can utilize a technique similar to that described for air embolism in the preceding paragraphs. During reflection of the chest skin, subcutaneous tissues, and muscles, the side "flaps" of the chest wall should be dissected laterally, farther than normal, such that "pockets" are formed between the rib cage and the outer flaps of reflected skin, subcutaneous tissue and muscle.

Care should be taken not to penetrate the rib cage/intercostal muscles during reflection. The pockets can then be filled with water. The pathologist can then perforate a submerged intercostal region (with a scalpel or needle) and look for air bubbles escaping from the pleural cavity. Measurement utilizing a water-filled, inverted graduated cylinder to "catch" the bubbles is possible, as described with air embolism above.

Depending on the case, it may be difficult for pathologists to identify specific vascular injuries. This is particularly difficult with high neck injuries and certain extremity injuries. One method that can aid in identification of vascular injuries makes use of a simple syringe filled with water. The syringe can be inserted into a portion of the blood vessel proximal to the area of concern. A relatively tight seal must be made around the syringe end. This can be accomplished with ones fingers, sutures, or a clamp. When the water is injected into the vessel, visualization of water escaping from the area of concern can be evidence that the vessel was indeed injured. If no water escapes, there is likely no injury. If water does escape, the pathologist should dissect the tissues further and visually identify the injury.

Special handling

If available for examination, the weapon used or suspected to have been used in a sharp force injury case can be examined, taking care not to compromise trace evidence or contaminate the weapon or the body. When examining a weapon, such as a knife, one should note if the blade is "single-edged" (having a single sharp edge, with the opposite edge being "blunt," or squared-off), "double-edged" (having 2 sharp edges), a combination of single and double edges (usually, these combination blades have 2 edges toward the tip and then become single-edged as the blade approaches the handle), and whether or not the blade is serrated (having teeth).

It is also important to note the length of the blade (measured from the base, where the handle begins, to the tip), the width of the blade (from one edge to the opposite edge), and the thickness of the blade. It should be noted that the terminology used to describe the dimensions of the knife and the wound do not correspond with one another. In other words, when comparing a stab wound to the weapon, the thickness of the blade produces the width of the wound, the width of the blade produces the length of the wound, and the length of the blade produces the depth of the wound.

Recognizing this, it should be noted that wound width does not necessarily equal blade thickness, wound length does not necessarily equal blade width, and wound depth does not necessarily equal blade length; because of the elasticity and flexibility of human tissues, as well as the fact that the weapon can move within the wound path, the wound width, length, and depth may actually be smaller or larger than the corresponding dimensions of the weapon.

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Histology and Microscopic Examination and Findings

Histologic examination in most routine sharp force injury deaths is probably not required, as gross autopsy findings are sufficient to explain death. Despite this fact, some offices/pathologists choose to perform microscopy on all cases. Sharp force injuries demonstrate extravasation of blood. Depending on the orientation of the tissue section, it may be possible to actually visualize a particular wound track. As with other injury types, cases in which death occurs many hours to days to weeks to longer following the initial sharp force injury may have histologic features which confirm clinical findings. Examples include areas of healing, organization of hematomas, pneumonia, and peritonitis.

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Photography and Documentation

As with other forensic case types, adequate photography and proper documentation is absolutely essential when performing a forensic autopsy on a sharp force injury case. As mentioned earlier, "as is" photographs may be in order. An identification photograph is required, as are photographs demonstrating the location and character of the injuries. Some pathologists choose to take photographs of the wounds before cleaning, but cleaned-up injury photos are absolutely required. There should be a sufficient number of photographs to show the general location of each wound, along with closer images to show more detail. A scale bearing the unique autopsy number should appear in a sufficient number of photographs so that, for any given photo, it is obvious that the photograph is of that particular case.

In addition to photographic documentation, additional written documentation should be made for every case. Autopsy notes and diagrams are prepared and retained by many pathologists. A formal autopsy report is absolutely required. It should contain sufficient written detail of the injuries such that the type, location, and extent of injuries are documented well enough that another pathologist would be able to adequately "reconstruct" the autopsy findings if asked to do so.

The suspected weapon should not be placed near the wound for photographic purposes as allegations of contamination by the victim's DNA could ensue should the case go to trial.

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Ancillary and Adjunctive Studies

Ancillary and adjunctive studies have previously been discussed in other sections of this article. Included here are issues related to postmortem radiology (looking for weapons and air embolism), trace evidence, sexual activity, blood spatter, clothing examination, and tool-mark impression analysis.

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Diagnostic Criteria

In this section, a variety of issues will be addressed, including circumstances that can make the identification of sharp force injuries difficult, injury types that actually represent a combination of sharp force and other injury types, and various entities which can mimic true, antemortem sharp force injuries.

Advanced decomposition may result in skin defects that mimic stab wounds. In reality, the skin is simply breaking down in relation to the decomposition process. It is important in such cases to carefully evaluate the tissues underlying the skin, to distinguish true sharp force injuries from decomposition. However, the tissues of victims of sharp force injury can certainly decompose. In such settings, the true injuries can become altered by the decomposition.

Decomposed body with multiple stab wounds. Note th Decomposed body with multiple stab wounds. Note the multiple decomposing stab wounds of the chest. Examination of underlying bones and cartilage can be very helpful in differentiating true sharp force trauma from artifacts produced by decomposition.
Stab wounds of the sternum of the decomposed body Stab wounds of the sternum of the decomposed body shown in the previous image.

Deaths related to animal attacks typically involve a combination of multiple injury types, including sharp and blunt force trauma. Domestic and wild animal attacks frequently involve multiple claw marks, which can be considered incised wounds, as well as bite marks, which can be considered stab/puncture marks combined with incised wounds and associated blunt force trauma.

This young child was mauled by a dog, with severe This young child was mauled by a dog, with severe sharp and blunt force injuries of the neck and face.
The dog suspected of attacking the boy shown in th The dog suspected of attacking the boy shown in the previous image was captured, euthanized, autopsied, and skeletonized. Discovering the victim's tissues within the dog's stomach and "matching" the dog's teeth to bite marks found on the child confirmed that the captured dog was, in fact, responsible for the child's death.

Postmortem sharp force injuries are typically characterized by a lack of vital tissue reaction. Because the heart is no longer beating when a postmortem injury is inflicted, the typical postmortem injury does not actively bleed, and therefore has a dry, yellow appearance, rather than a red, bloody appearance. Occasionally, a postmortem injury will have an appearance that mimics a true antemortem injury in that it appears red; this typically results from the injury occurring in an area of lividity, where blood settles due to gravity into the dependent (lower) portions of the body. Conversely, an antemortem incised wound can appear bloodless when the victim has been immersed in water for a period after death.

The incised wounds depicted in this photo were inf The incised wounds depicted in this photo were inflicted after the elderly victim was killed via sharp and blunt force of the head and neck. Note the lack of vital tissue reaction in the chest and abdominal wounds.

Medical intervention can mimic true antemortem sharp force injuries or mask existing true injuries. When medical care providers are attempting to save a victim's life, preserving forensic evidence is not necessarily at the top of their priority list. As such, stab and other wound types may be cut through by surgeons as they attempt life-saving operations. In addition, placement of needles, chest tubes, and other medical devices can introduce additional sharp force skin defects.

A previously sutured surgical incision is shown af A previously sutured surgical incision is shown after stitch removal and reapproximation of the surgical margins by superglue. The defect above the left side of the scale is a stab wound. Note that it had been incorporated into the surgical incision (and was not recognizable with the stitches in place). The horizontal defect above the right side of the scale also appears to be a stab wound; however, this defect had actually been produced by emergency personnel during chest tube placement.

A variety of other defects can mimic true, antemortem, sharp force injuries. Examples include embalming artifacts, lacerations (blunt force trauma), and decapitation injuries from sudden deceleration.

A laceration (from blunt force trauma) of the neck A laceration (from blunt force trauma) of the neck mimicking a sharp force injury. The margins of the wound are quite clean, similar to a sharp force injury; however, there is tissue bridging evident.
Decapitation injuries may or may not represent tru Decapitation injuries may or may not represent true sharp force injuries in that they can occur as a result of contact with a sharp edge or as a result of sudden deceleration with or without associated blunt force impact. This photo shows an incomplete decapitation injury caused by high-speed impact with a cable while the victim was driving a recreational vehicle.
Multiple postmortem, trocar "stab wounds" of the h Multiple postmortem, trocar "stab wounds" of the heart produced during embalming.

Although there are a variety of skin defects that can mimic sharp force injuries, it is important to also recognize that sharp force injuries can sometimes be mistaken for other injury types. The best example is when a victim has gunshot or shotgun wounds as well as sharp force injuries. In such cases, stab wounds are most likely to be mistaken for projectile exit wounds, and vice versa.

The victim in this photograph was stabbed and shot The victim in this photograph was stabbed and shot multiple times; the photo shows a gunshot entrance wound (lower wound), as well as a stab wound (upper wound). As the victim also had gunshot entrance wounds on his back, and the presence of distinct sharp force injuries was not immediately apparent, the upper wound was originally interpreted as a gunshot exit wound.
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Common Misconceptions

Despite what is portrayed in Hollywood, forensic pathologists are usually unable to determine the direction of infliction of an incised wound. In other words, it is unusual that examination of the wound allows one to determine if the wound was inflicted in a right-to-left direction or a left-to-right direction. Some "experts" contend that the overall shape and appearance of the wound allows for such determination. This is not true.

Occasionally, small skin tags/lacerations or abrasions along the wound margins or near the angles may allow for determining the direction of infliction (similar to how a bullet direction can be ascertained in graze gunshot wounds), but this is the exception rather than the rule. The medical examiner can only comment on the path of the blade through the body and the structures injured, not the relationship of the victim and assailant at the time of injury.

An incised wound complex of the anterior neck. Not An incised wound complex of the anterior neck. Note that there are multiple wound angles on each side, indicating that multiple cuts were inflicted in this homicide. The direction of infliction (ie, right to left or left to right) could not be determined in this case.

Another myth that is perpetuated by Hollywood is the belief that the forensic pathologist is able to determine the handedness of the assailant. Some depictions go so far as to suggest that pathologists might also be able to say with certainty that the attacker was behind or in front of the victim. For any scenario offered as an explanation for a particular wound pattern, there are typically several other scenarios that are equally as possible. For example, a person might suggest that the wound depicted in the above image was the result of a right-handed assailant standing behind the victim and pulling the knife across the front of the victim's neck, from left to right, while holding the knife with the right hand. Although that scenario may explain the injuries, it is equally as possible that the attacker was facing the victim, holding the knife in the left hand, and slashing the victim with a backhand motion, from the victim's left to right.

A final series of misconceptions was previously addressed. To review, with stab wounds, the length of the knife blade is responsible for producing the depth of the wound, but wound depth does not necessarily equal blade length. The wound depth can be less than, equal to, or even greater than the blade length. The blade width produces the wound length, but the wound length can be less than, equal to, or greater than the blade width. Finally, the blade thickness produces the wound width, but the wound width can be less than, equal to, or greater than the blade thickness. The flexibility and elasticity of the human body are responsible for these variations. It is worth noting that pouring radio-opaque materials or plaster into stab wounds will not produce an accurate outline of the dimensions of the weapon used to inflict the injuries.

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Issues Arising in Court

Some of the issues that may arise in court have already been discussed, namely the direction of infliction of an incised wound and the handedness of an attacker. To briefly review, it is generally not possible for a pathologist to determine either of these issues with any reliable degree of certainty.

Another issue that sometimes arises in court proceedings is the question of wound sequence. In other words, is it possible to determine whether or not a given wound occurred before or after a separate wound?

In a vast majority of cases, this is not possible. However, there are at least 3 exceptions to this rule of thumb, as follows:

  1. If there are 2 wounds, with one being obviously antemortem in appearance on external exam (having a vital tissue reaction) and having associated internal antemortem injuries, and the other wound has a postmortem appearance (dry and yellow), with little internal injury, then the obvious conclusion is that the antemortem wound occurred first.
  2. If wound A has associated bone fractures with a fracture line extending to and ending when it runs into a fracture line that is associated with wound B, then wound B preceded wound A.
  3. Occasionally, information regarding the historical events of the case in conjunction with autopsy findings allows one to determine the sequence of wounds.

For example, a man is found at autopsy to have 2 stab wounds, one on the upper right arm that transects the brachial artery and one in the upper midline neck, which transects the upper cervical spinal cord. At the scene where the body was found, the man was found in the kitchen lying in a pool of blood. There is blood spatter and drip marks in the living room, with trailing blood through the dining room and into the kitchen. The blood is determined to be that of the victim. Because it would not be possible for the victim to move following the spinal cord transection, it is obvious that the arm stab wound occurred before the neck stab wound and that it occurred in the living room.

Another issue that occasionally arises in court is the question of how long a person survived following infliction of the wound(s). This question is very difficult to answer with any degree of certainty. [4, 5] The average adult male is said to have about 5 liters of blood. The rapid loss of about 33% of the blood volume can result in shock and death. The average cardiac output is between 4.5 and 5.0 liters per minute, but this changes drastically in situations in which a person sustains serious injury. The injury itself and the fear associated with the circumstances will increase the potential cardiac output tremendously.

Now, attempt to calculate the amount of blood loss that occurs from each of the sharp force injuries, recognizing that there may be reflexive vascular constriction in response to the injury (or in response to shock). It becomes obvious very quickly that there are much too many variables to easily determine an estimated time of survival that is accurate. Pathologists may be able to give rough estimates based on experience. Alternatively, pathologists may provide a best "guesstimate" using the factors described above. If such a "guesstimate" is provided, the pathologist should give a wide range and acknowledge that there are so many variables that an accurate estimate is really not possible.

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