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Postmortem Changes

  • Author: S Erin Presnell, MD; Chief Editor: J Scott Denton, MD  more...
 
Updated: Oct 13, 2015
 

Overview

After death, a sequence of changes naturally occurs in the human body. Although these changes proceed in a relatively orderly fashion, a variety of external factors and intrinsic characteristics may accelerate or retard decomposition. Understanding common postmortem changes and the variables that affect them allows the forensic pathologist to more accurately estimate the postmortem interval (PMI) and to provide a time frame during which death occurred. Further, an awareness of common postmortem artifacts limits the risk of misdiagnosis at the time of autopsy.

History

Death and the changes that follow have been ingrained in society since the dawn of history. Ancient Egyptians took extraordinary measures to slow decomposition, with some good results. Later societies recognized the need to sequester the dead from the living to contain the spread of disease. In modern times, bereaved families must choose between cremation and embalmment for their dearly departed. Death is a part of life,and decomposition is a part of death.

Epidemiology

All bodies undergo some degree of postmortem change after death. Change begins at the molecular level and sequentially progresses to microscopic and gross morphology.

Overview of the entity

Postmortem changes begin soon after death and progress along a timeline. Two processes, putrefaction and autolysis, begin to alter the body; either one may predominate, depending on the circumstances surrounding death, as well as the climate. Putrefaction involves the action of bacteria on the tissues of the body. This process, prevalent in moist climates, is associated with green discoloration of the body; gas production with associated bloating; skin slippage; and a foul odor.

Autolysis is the breakdown of the body by endogenous substances. It proceeds most rapidly in organs such as the pancreas and stomach. It may predominate in more arid conditions and can eventually result in mummification.

In most circumstances, autolysis and putrefaction occur in tandem. In temperate climatic conditions, they can result in rapid degradation of the tissues. These alterations may eventually produce great distortion of the body after death, hampering the interpretation of the postmortem findings but not ameliorating the value of the autopsy.

Some of the more well-known postmortem changes, such as rigor mortis, livor mortis, and algor mortis, progress on a relatively set schedule; however, many external and intrinsic factors may affect their development. It should be remembered that the estimated period for the arrival and passage of these manifestations of the decomposition process is based on studies under very controlled conditions, including a temperate climate (ie, 75° F).[1]

In reality, many deaths occur outside of these “ideal” settings, and additional confounding variables may be present (eg, layered clothing, obesity, fever). Further, the longer the PMI, the less accurate the PMI estimate becomes.

Indications for the procedure

Postmortem changes may partially obscure antemortem trauma and disease or mimic their presence. It is essential that the pathologist recognize these findings for what they are. Despite the degradation the body undergoes during the postmortem period, a complete autopsy of a decomposing body often yields abundant information.

Although there is quite a lot of variability in the time schedule of common postmortem changes, all bodies eventually decompose to some degree. The physical and biochemical alterations, when considered in concert with a thorough medicolegal death investigation, may allow one to estimate the PMI. Estimation of the time of death is a critical component of forensic death investigations, but it is an imperfect science. Unless a death is witnessed, it is usually possible to provide only a time window during which death could have occurred.

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Definitions

Rigor mortis is the postmortem stiffening of the body’s muscles. It may or may not involve some degree of actual shortening of the muscles. In most cases, rigor mortis begins within 1-2 hours after death; it begins to pass after 24 hours (see the image below).

The decedent shows persistent rigor mortis with th The decedent shows persistent rigor mortis with the right arm defying gravity. The body must have been in another position for several hours after death before being placed in a supine position.

Livor mortis is the purple-red coloration that appears on dependent portions of the body other than areas exposed to pressure after the heart ceases to beat. It results from the settling of the blood under the force of gravity (see the image below).

Livor mortis on the posterior aspects of the body Livor mortis on the posterior aspects of the body is caused by settling of the blood because of gravity when the body is in a supine position.

Tardieu spots are petechiae and purpuric hemorrhages that develop in areas of dependency secondary to the rupture of degenerating vessels under the influence of increased pressure from gravity (see the following 2 images).

As the postmortem interval lengthens, Tardieu spot As the postmortem interval lengthens, Tardieu spots develop in areas of lividity, such as this individual's shoulder area, as decomposing capillaries rupture.
Tardieu spots on the abdomen. Tardieu spots on the abdomen.

Algor mortis is the process by which the body cools after death. Cooling takes place only if the ambient temperature is cooler than the body temperature at the time of death.

Tache noire is the dark, red-brown stripe that develops horizontally across the eyes when the eyelids are not closed after death. It is a drying artifact that may mimic trauma (see the image below).

Tache noire develops when the eyelids are not comp Tache noire develops when the eyelids are not completely shut and postmortem drying occurs.

Purge fluid is decomposition fluid that may exude from the oral and nasal passages as well as other body cavities (see the image below).

Postmortem purge fluid exudes from the oral and na Postmortem purge fluid exudes from the oral and nasal passages; no traumatic injuries were uncovered at autopsy.

Decomposition is the postmortem process of endogenous autolysis and putrefaction from external and primarily internal bacterial sources (see the image below).

Decomposition is a process of autolysis and putref Decomposition is a process of autolysis and putrefaction.

Maceration is an autolytic postmortem process that occurs in intrauterine deaths. It is caused by endogenous enzymes; putrefactive bacteria are not a factor (see the image below).

Maceration after retention of an intrauterine feta Maceration after retention of an intrauterine fetal death.

Postmortem interval is the time since death.

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Scene Findings

Findings at a scene are extraordinarily helpful in the assessment of postmortem changes. The environment, in particular the temperature, influences the rate of decomposition; higher temperatures hasten the process. It should be remembered that there may be a variety of microclimates within the same locale that can influence postmortem changes (eg, the body may have lain below an air conditioning vent). When estimating the time of death, the gross findings must be correlated with the prevailing environmental factors. The influence of local fauna must also be considered. The presence of insects or signs of animal activity near the body may be correlated with tissue defects resulting from postmortem carnivorous feeding.

Rigor mortis may develop very rapidly if the body is acidotic at the time of death. Signs of a struggle may explain accelerated rigor mortis, because rigor mortis is related to a drop in pH within myocytes. In some cases, rigor mortis or livor mortis may appear in patterns inconsistent with the effect of gravity at the scene. This indicates that the body was moved (either by early responders or someone else) before the investigator assessed the body. It may indicate that the body has been transported from another crime scene.

Circumstantial time markers may assist in narrowing the postmortem interval. For example, the date of the oldest newspaper on the front doorstep may indicate that the decedent died before the delivery of that newspaper (provided the person regularly picked up the newspaper). A person found dead wearing pajamas in the kitchen with a bowl of cereal on the table suggests that death occurred in the morning. An automated teller machine (ATM) receipt found in the clothing of a decomposing body suggests to investigators that the decedent was alive at the time and date that appears on the receipt. Similarly, the time and date that a final email or text message was sent may be helpful in assisting in the estimation of the PMI.

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Trace Evidence

Advanced postmortem changes may obscure or destroy some trace evidence. Hairs and fibers may be lost as the upper layers of skin slough. The presence of soot or stippling around a gunshot wound may also be difficult to assess on sloughed, discolored skin. During the early PMI, however, valuable trace evidence may persist, including the presence of sperm and prostatic acid phosphatase in sexual assault cases, although such evidence does degrade with time.[2]

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Gross Examination and Findings

Rigor mortis develops as the body’s energy source (adenosine triphosphate [ATP]) is depleted. Muscle fibers require ATP for relaxation; once depleted, actin and myosin proteins remain complexed, resulting in stiffening of the muscles. Rigor mortis is thought to develop in all muscles simultaneously; however, it is most evident first in the smaller muscle groups, such as the jaw, after which rigor mortis typically occurs in the upper extremities and then the lower extremities, as in the following image.

The decedent shows persistent rigor mortis with th The decedent shows persistent rigor mortis with the right arm defying gravity. The body must have been in another position for several hours after death before being placed in a supine position.

Rigor affects both smooth and skeletal muscles, including the myocardium (simulating hypertrophy), hair follicles (resulting in cutaneous "goose bumps") (see the image below), and seminal vesicles (resulting in postmortem semen release from the penile meatus).

Rigor mortis of the erector pilae can result in po Rigor mortis of the erector pilae can result in postmortem "goose flesh."

Rigor mortis first appears approximately 1-2 hours after death. Progressive stiffening occurs for approximately 12 hours, persists for approximately 12 hours, then diminishes over the next 12 hours as tissues break down as a result of autolysis and putrefaction.

Rigor mortis may be used to deduce the position of the decedent if the body has been moved after the development of rigor mortis. If rigor mortis is broken by manipulation before becoming fully fixed, it may reform in the new position.

The estimation of the strength of rigor mortis is often rated on a scale of 0–4 and is highly subjective.

Cadaveric spasm is an uncommon and disputed form of rigor that develops immediately upon death, usually after strenuous activity. One theoretical example would be a drowning victim’s hand clutched around a swatch of grass growing on the water’s edge. In such cases, it is presumed that the decedent was in profound lactic acidosis at the time of death as a result of violent struggle and went into rigor mortis immediately.

Livor mortis usually appears 30 minutes to 2 hours after death, though it may appear sooner in cases of severe heart failure in which the antemortem circulation was sluggish. After a PMI of 8–12 hours, red cells extravasate from the vessels into the surrounding soft tissue. Until that time, the application of pressure to an area of livor will result in blanching of the skin (as depicted in the image below).

Pressure on unfixed livor results in blanching of Pressure on unfixed livor results in blanching of the coloration.

After that period, livor may blanch with forceful pressure but will eventually not blanch, at which time it is considered fixed. Movement of a body before the complete fixation of livor will result in the redistribution of lividity into the newly dependent areas of the body. If there is partial fixation of the livor at the time the body is moved, it is to be expected that the original pattern of distribution of residual livor would remain, as shown in the following image.

Livor mortis in an anterior position. The area of Livor mortis in an anterior position. The area of blanching across the chest and abdomen resulted from the decedent lying on top of his left arm and right hand.

Livor mortis also affects the organs; it is often most appreciated in the lungs, which appear congested in dependent areas (see the following image). In appearance, livor may differ markedly from case to case. It may be difficult to discern lividity in darkly pigmented individuals and in cases in which near exsanguination has occurred.

The lung is dark purple in the posterior dependent The lung is dark purple in the posterior dependent areas as a result of livor mortis. This may simulate congestion.

Livor has become particularly important in determining the postmortem position of infants (eg, prone sleeping position) when first responders have moved the decedent before the arrival of agency investigators. As breakdown of tissues, including the vasculature, progresses, red cell extravasation into the soft tissues may actually simulate antemortem hemorrhage, as demonstrated in the image below. Differentiation is made in the context of the location and pattern of the discoloration and the events surrounding the death. In some cases, it may not be possible to differentiate antemortem trauma from postmortem artifactual effects.

Decomposition has progressed in this individual wi Decomposition has progressed in this individual with breakdown of blood vessels and extravasation of red blood cells into the subcutaneous and adipose tissues of the abdomen, simulating antemortem hemorrhage. There were no associated cutaneous or bony injuries, and the scene was innocuous.

Tardieu spots develop in areas of dependency, hence, in areas of livor. They occur secondary to the rupture of vessels under the influence of increased pressure from gravity in conjunction with vascular breakdown (see the following 2 images). Classically, they are seen in cases involving hangings; they appear on the lower legs of individuals who have been fully suspended, although they may be seen in any area of dependency.

As the postmortem interval lengthens, Tardieu spot As the postmortem interval lengthens, Tardieu spots develop in areas of lividity, such as this individual's shoulder area, as decomposing capillaries rupture.
Tardieu spots on the abdomen. Tardieu spots on the abdomen.

Tardieu spots may be confused with premortem petechiae or purpuric hemorrhages. An analogous process may occur in the conjunctiva and sclera, as is sometimes seen in cases in which a person dies in a position in which the head hangs downward off of a bed. In these cases, the conjunctiva and sclera are injected, and hemorrhage may become confluent; nevertheless, attention should still be paid to antemortem causes of ocular hemorrhages.

Algor mortis is the process by which the body cools as heat production ceases and body heat is lost to the environment. Bodies in which the ratio of the surface area to body mass is large cool more quickly (eg, bodies of thin people and infants cool more quickly than bodies of obese persons).

There are several formulas for estimating the rate of postmortem cooling; however, with all these formulas, it is assumed that death occurs in temperate conditions and that the decedent had normal antemortem body temperature (ie, the antecedent body temperature actually varies from 93.74°–100.04° F, as determined rectally).[3]

These formulas tend to give a sense of scientific accuracy to the examination and can be misleading. A general rule of thumb is that the body loses heat at an average of 1.5°-2° F during the first 12 hours after death .[4] However, the rate of cooling is dramatically affected by the circumstances of death, most significantly, by the environmental and body temperatures. A body will only cool to the environmental temperature; a body lying in 105° F during the summer would not be expected to cool at all—in fact, in such circumstances, the body’s temperature would increase.

Other significant factors affecting algor mortis include the body location (eg, shade versus sun), clothing, and the habitus of the decedent. A cold tile floor would promote body cooling as a result of conduction. Obese individuals and heavily clothed individuals would be expected to lose heat more slowly.

Purge fluid is foul smelling, red-brown fluid that may exude from the oral and nasal passages as decomposition progresses, as depicted in the image below. It often flows after pressure is exerted on the body, either from the presence of gases that result from internal decomposition or following manipulation of the body. Purge fluid may simulate antemortem hemorrhage, but no traumatic injuries will be detected at autopsy.

Postmortem purge fluid exudes from the oral and na Postmortem purge fluid exudes from the oral and nasal passages; no traumatic injuries were uncovered at autopsy.

Tache noire is horizontal darkening of the exposed sclera that occurs secondary to drying when the eyelids are left partially opened after death. The characteristic location along the parted eyelids is instrumental in interpreting this finding (see the image below).

Tache noire develops when the eyelids are not comp Tache noire develops when the eyelids are not completely shut and postmortem drying occurs.

Other mucus membranes, such as the lips and tongue, may also darken and appear hemorrhagic when dried. Incisions into the underlying tissue will reveal no hemorrhage (see the following image).

Postmortem drying of the tongue and mucosal membra Postmortem drying of the tongue and mucosal membranes darkens the tissues, imparting a pseudohemorrhagic appearance.

Gastric emptying refers to the process of digestion after consumption of a meal. Depending on the size and composition of the meal, emptying of the stomach may occur over a period of ½ to 6 hours or, in some cases, much longer. Stress may delay normal digestion. The presence of stomach contents may be most helpful if the contents are recognizable and if it is known when the decedent consumed that particular meal. It is not a reliable indicator of the PMI.

Decomposition is a process of endogenous autolysis and putrefaction, primarily from intestinal microorganisms. The bacterial flora disseminates, owing to the fact that the body no longer has a functional immune system. The abdomen develops a green discoloration after 24–36 hours, usually in the right lower quadrant first (the location of the microbe-laden cecum). An example of this is below.

Early decompositional changes are manifested by gr Early decompositional changes are manifested by green discoloration over the abdomen.

Marbling may develop with the delineation of the vasculature as a result of the reaction of hydrogen sulfide produced by bacteria with hemoglobin from the lysis of erythrocytes, as shown below. Bloating of the body occurs as a result of bacterial gas production; in intemperate conditions, bloating occurs over a period of 2–3 days. Bloating causes distortion of both the body and face.

Marbling outlines the vasculature in this decedent Marbling outlines the vasculature in this decedent as the postmortem interval lengthens.

Gas (eg, hydrogen sulfide, methane) forms in the organs and subcutaneous tissues as well as the body cavities. Epidermal vesicle formation and skin slippage occur as the epidermis separates from the underlying dermis. The body becomes diffusely discolored green-black, often obscuring the race of the decedent (see the following image).

Decomposition advances with green discoloration of Decomposition advances with green discoloration of the skin, generalized bloating (beginning in the abdomen), and vesicle formation with subsequent skin slippage.

Degloving of the skin of the palms and soles typically occurs during decomposition, as well as in cases involving thermal exposure (ie, fires) and immersions (see the following example).

Postmortem degloving of the hand. Postmortem degloving of the hand.

The epidermis commonly retains enough ridge detail to allow fingerprints to be obtained, which assists in the identification of the decedent, as demonstrated below.

A law enforcement official utilizes the degloved f A law enforcement official utilizes the degloved fingers to obtain fingerprints.

Internally, organs disintegrate at different rates. The pancreas, adrenal glands, and gastrointestinal mucosa show marked autolysis early in the PMI (see the following images). Indeed, with its digestive enzymes, the pancreas may show early breakdown of its vasculature; to the inexperienced examiner, seepage of red blood cells may mimic hemorrhagic pancreatitis.

View of collapsed, decomposing organs in the chest View of collapsed, decomposing organs in the chest cavity with maggots present and gaseous distention of the intestines.

The uterus and prostate resist decomposition the longest, owing to the amount of fibromuscular tissue in these organs.

The brain turns a pink-gray color and undergoes liquefaction over a period of weeks. Fat may also liquefy, as seen in the following image. Small, white calcium soap granules may develop on the epicardial and endocardial surfaces of the heart, and the intima of the vasculature turns a dusky purple as a result of red cell hemolysis.

Liquefied fat draining into the chest cavity. Liquefied fat draining into the chest cavity.

Other potential artifacts of decomposition simulating antemortem illness or trauma include rupture of the stomach or esophagus, "hemorrhage" in the posterior neck anterior to the vertebrae, and extravasation of blood into the soft tissues in areas of dependent lividity.

Factors accelerating decomposition include sepsis, heat (ie, environmental heat and body temperature), and processes that promote heat retention. Of note, bodies submerged in water decompose at a slower rate than those on land that are exposed to air. Bodies buried in the ground have the slowest rate of decomposition, owing to the typically cooler temperatures underground and the relative inaccessibility of the body to environmental predators.

Two less common variants of decomposition are mummification and adipocere formation. The former process occurs in warm, dry environments where the tissues rapidly desiccate and resist the typical "wet" decomposition. With mummification of the body, external injuries may be preserved, though the size of wounds may be distorted, as demonstrated below.

Mummification of this homicide victim occurred aft Mummification of this homicide victim occurred after she remained in a secure bedroom in August in the southeastern United States for almost 2 weeks with no air conditioner. Mummification preserved the numerous stab wounds and incised wounds, allowing accurate postmortem assessment of her injuries.

Adipocere formation typically occurs in bodies submerged in water or in warm, humid environments. The tissues are converted into a waxy, pasty material as a result of the reaction of clostridial enzymes with tissue fatty acids, as seen in the following image.

Adipocere has developed in this person who was sea Adipocere has developed in this person who was sealed in a barrel containing water and buried for over 5 years.

Organs converted into adipocere resist degradation and are frequently present for postmortem examination (see the image below); however, the tissues are extremely friable and will often crumble upon manipulation.

Although waxy, the internal organs resist putrefac Although waxy, the internal organs resist putrefaction when converted to adipocere.

It is not uncommon for mummification and adipocere formation to affect localized areas of the body that would otherwise undergo the usual decompositional changes (eg, mummification of the fingers and toes is commonplace). An example of this is below.

Isolated mummification may be evident in areas of Isolated mummification may be evident in areas of the body with less tissue mass, such as the nose, ears, hands, and feet.

A dramatic component of the spectrum of postmortem change results from exposure of the body to insect activity. In North America, the deposition of fly eggs on human remains and the ensuing maggot activity can be traced to the blowfly, as seen below.

The decedent demonstrates almost complete skeleton The decedent demonstrates almost complete skeletonization of the head as a result of maggot activity.

The defects caused in human tissues by insect larvae (eg, maggots) may mimic true injury. Additionally, the blood and exposed tissues in antemortem wounds attract insects, whose activities distort antemortem lesions and, in some cases, obscure their characteristics or presence. Blowflies usually lay eggs in temperatures higher than 50° F in daylight hours within hours of death when they have access to bodies (see the following image).

Fly eggs, which resemble Parmesan cheese, accumula Fly eggs, which resemble Parmesan cheese, accumulate on moist areas and accessible orifices of the body.

The eggs hatch in 1–2 days. The larvae (ie, maggots) consume tissue and grow through 3 larval stages, known as instars, as demonstrated in the image below.

Young maggots resemble fly eggs but are mobile. In Young maggots resemble fly eggs but are mobile. In this case, fly eggs were laid in the moist environments of the partially open eyes, nares, and mouth. The eggs hatched and migrated across the face.

The proteolytic enzymes secreted by large numbers of maggots work to increase the rate of tissue breakdown. The larvae pupate in approximately 1-2 weeks; adult flies emerge in another 2 weeks, as seen in the following 2 images. These timelines, however, vary greatly with the species and environmental factors; in some cases, a forensic entomologist may need to be consulted to assist in estimating the PMI.

Fly pupae such as these are often recovered away f Fly pupae such as these are often recovered away from the body, because maggots migrate before pupation; these should be recovered from the death scene if the time of death is in question.
Fly pupae on a decedent; note the presence of othe Fly pupae on a decedent; note the presence of other insects.

Insect predation by roaches and ants may occur at any stage during the PMI. They typically produce yellow-red, irregular abrasions, which usually may be recognized by their grouped pattern on the body (see the image below). Ants themselves may consume fly larvae and slow the rate of decomposition.[5]

Postmortem ant and roach activity leaves a typical Postmortem ant and roach activity leaves a typical grouped pattern of postmortem "abrasions."

Carnivores such as rodents, cats, dogs, and vultures may feast on a body. Rodent activity is typified by a yellow-based defect, often with scalloped edges (see the images below).

This individual was recovered in a home with rats. This individual was recovered in a home with rats. Postmortem bite marks are yellow, bloodless defects with scalloped edges. Top: Third metacarpal and proximal phalanx. Bottom: Fifth metacarpal and proximal phalanx.

Canine activity also results in yellow defects; gnaw marks may be apparent on the underlying bones, as shown below.

Postmortem gnaw marks on a long bone. Postmortem gnaw marks on a long bone.

Vultures create cutaneous defects and may consume internal organs through surprisingly small openings in the skin. Beak marks may be evident around the cutaneous defects, as demonstrated below).

Postmortem vulture activity on the leg of a woman Postmortem vulture activity on the leg of a woman recovered in a wooded area; the underlying tendon is exposed, and much of the musculature is absent. Irregular, yellow defects around the deeper wound are consistent with beak marks.

Bodies recovered from open water commonly demonstrate the feeding activity of marine life (eg, fish, crabs, shrimp) on the fleshy parts of the body such as the lips, eyelids, and ears (see the example below).

Postmortem tissue consumption caused by small mari Postmortem tissue consumption caused by small marine animals such as fish and crabs on the dorsal hand. The edges of the defects are typically scalloped.

Larger marine life such as alligators and sharks may produce defects that mimic antemortem sharp and blunt force injuries, as demonstrated in the following image. Although these postmortem defects are typically yellow, blood seepage into these areas may cause these defects to resemble antemortem trauma. Conversely, water may wash clean antemortem soft-tissue hemorrhage, causing a true injury to resemble an artifact.

Larger marine life such as sharks and alligators m Larger marine life such as sharks and alligators may consume large amounts of tissue and leave sharp injuries in the soft tissue and/or bone. In such cases, it may be difficult to determine whether the injuries represent antemortem trauma or postmortem artifacts.

Skeletonization usually requires months to occur in temperate conditions, but it may develop in less time if larger predators have access to the body (see the following image). Larger predators may remove body parts and create postmortem artifacts, such as gnaw marks on bones. The application of anthropologic studies is helpful in assessing the decedent’s gender, race, size, and age. Unless antemortem injuries affect the bony structures, evidence of the cause of death in some cases may be completely lost as a result of skeletonization and the loss of soft tissue.

This skeleton is that of an adult man who had been This skeleton is that of an adult man who had been missing for 1.5 months during the late fall in the southeastern United States. He was found in a wooded area. Although the skeleton was mostly intact, gnaw marks were evident on several ribs.

Maceration is a process that occurs in cases of intrauterine demise, as shown in the following image. It is an autolytic process noticeable several days after an intrauterine death caused by endogenous fetal enzymes; because the fetus is typically sterile, putrefactive bacteria usually do not play a role. Exceptions include cases in which the fetus had an infection, such as chorioamnionitis or congenital pneumonia; in such cases, the fetus may show more characteristic signs of decomposition.

Maceration after retention of an intrauterine feta Maceration after retention of an intrauterine fetal death.

Typically, the macerated fetus shows dark pink to brown discoloration of the skin, followed by skin slippage without gaseous bloating. As maceration progresses in utero, joints loosen and the skull plates separate; characteristically, the skull plates override their sutures, which to the inexperienced examiner may mimic head trauma. Once expelled from the uterus, the fetus or infant may become colonized by environmental bacteria, adding a putrefactive component to subsequent postmortem changes.

The presence of maceration may be used as proof of an intrauterine fetal death. The absence of maceration, however, does not exclude an intrauterine death, because it takes some time to develop.[6] Another process that commonly occurs in cases of infant mortality is the postmortem subcutaneous congealing of fat after the body is refrigerated; the resultant doughy consistency of the tissue may simulate a ligature mark around the neck, as shown below).

Congealing of subcutaneous adipose tissue on the n Congealing of subcutaneous adipose tissue on the neck of an infant may mimic trauma.

Embalming, which involves the administration of fixative fluids and/or powders into the body, slows the process of decomposition dramatically. However, embalming introduces its own artifacts, including cutaneous incisions to gain vascular access, typically on the lateral neck and/or groin, and trochar defects on the abdomen with associated internal organ disruption. An example is shown below. The visceral defects are characterized by the absence of hemorrhage and the absence of histologic reactive changes.

Trochar hole in an embalmed decedent (button remov Trochar hole in an embalmed decedent (button removed).

Wiring of the jaws may hamper oral examination. Caps over the eye globes must be removed to assess ocular findings. Cosmetic creams used on the skin may obscure antemortem injuries. Embalmed bodies that have been buried and subsequently exhumed commonly show cutaneous fungal growth, especially in wet environments, as depicted in the following image. With the passage of time, adipocere may develop.

Fungal growth on a previously embalmed and subsequ Fungal growth on a previously embalmed and subsequently exhumed body.

Special dissections

Decomposition does not preclude the possibility of performing a complete autopsy. Tissues such as liver, spleen, skeletal muscle, kidney, and brain may be used for toxicologic analysis if blood is not available. Long bone segments, including the marrow space, teeth, and skeletal muscle, are useful for DNA analysis.

Special autopsy procedures

Imaging studies

It is advisable to obtain radiographs of body regions in a decomposing body when potential trauma cannot be assessed. These usually include areas in which tissue was lost as a result of insect or animal activity. Imaging studies allow the pathologist to find projectiles or radiopaque fragments in the body in cases in which the decedent sustained a gunshot wound or was assaulted with a metallic object (eg, a knife). However, the absence of radiopaque fragments does not exclude the possibility of an assault.

Radiographs are also useful in the identification of decomposed remains (eg, facial sinus configuration, orthopedic hardware). Postmortem CT scans can be useful in documenting injuries and disease in decomposed bodies. They are particularly useful in identifying intracranial pathology before removal of the cranium.

Insect collection

It is extremely helpful to involve an entomologist in cases involving insect activity; entomologists can provide information as to the type of insect(s) and the stage of the insect life cycle at the time of discovery. The selection, handling, and storage of the insects present on and around the body must be properly carried out for data to be useful. Insects at all stages of development present at the time of discovery of the body should be killed and preserved; some should also be retained alive with a food source for subsequent evaluation. Also, the characteristics of the environment in which the decedent was found must be documented and the ambient temperature recorded to assist in predicting the insects’ maturation rate in those particular circumstances.

Special handling

Standard precautions should be utilized when performing an autopsy of any individual, regardless of the extent of decomposition. In all cases, it is wise to ensure proper autopsy room ventilation. The pathologist should proceed with some degree of care during the autopsy of a decomposing individual, because tissues become more delicate as the PMI progresses. Indeed, it is not unusual for the brain to be intact at the time the calvarium is removed and to then disintegrate completely as a result of disruption of the arachnoid membrane supporting the liquefying parenchyma when an attempt is made to remove the brain.

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Histology and Microscopic Examination and Findings

Histology may assist in discriminating a postmortem artifact from an antemortem injury by documenting the presence or absence of an inflammatory response.[7] However, in significantly decomposing tissues, histology reveals extensive autolysis and bacterial overgrowth, which hampers histopathologic interpretation of both disease and trauma. In some cases, a trichrome stain may be useful in confirming myocardial fibrosis or cirrhosis.

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Photography and Documentation

As in all forensic cases, photographs of the decedent taken at the scene documenting the position of the body when discovered (when possible) are valuable adjuvants to the interpretation of the postmortem findings and changes. Photographs of all pertinent positive and negative findings may address questions that arise as the case unfolds. Photography and diagrams supplement the written descriptions contained in the final autopsy report.

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Ancillary and Adjunctive Studies

Vitreous fluid, if available, may be evaluated for the presence of several analytes, including sodium, potassium, chloride, urea nitrogen, creatinine, glucose, and ketones/acetone. Immediately after death, vitreous analyte levels reflect terminal antemortem serum concentrations better than postmortem blood samples do, owing to the fact that vitreous fluid is contained within the eye and is partially protected from the byproducts of cellular autolysis. Urea nitrogen and creatinine levels show the most postmortem stability; sodium and chloride levels are relatively stable over the early PMI but decline as decomposition progresses. Typically, markedly decreased levels of sodium and chloride and a markedly increased potassium level are reflective of decomposition.

The glucose level declines rapidly during the PMI; a concentration of zero is not unusual in a healthy individual who succumbed to traumatic injuries. However, high levels may reflect a diabetic state. The presence of acetone and/or ketones in the ocular fluid substantiates a diagnosis of diabetic ketoacidosis in cases in which the glucose level is elevated. In the absence of a high glucose concentration, their presence may indicate starvation.[8]

Vitreous fluid potassium levels have been shown to steadily increase after death; the vitreous fluid potassium level may be used to help estimate a PMI in temperate conditions. However, the existing formulas are restricted by confidence limits of almost +/- 1 day; all are best utilized in the first 100 hours from the time of death. Numerous other variables affect the vitreous potassium level, including antemortem serum levels and the aforementioned conditions promoting accelerated decomposition. In temperate conditions, vitreous fluid is typically not retrievable after approximately 4 days.

Vitreous fluid concentrations of some compounds, including alcohols and some medications, are reflective of serum levels 1–2 hours before death. Comparisons of vitreous fluid concentrations with serum levels may be of value in assisting the determination of the manner of death in overdose cases.[1] For example, significantly higher drug concentrations in the postmortem blood, as compared with the drug concentrations in vitreous fluid, suggest an acute overdose (possibly suicide) rather than chronic overconsumption of the medication (which would likely be accidental). It should also be remembered that putrefaction may result in ethanol formation in the tissues and blood as the PMI lengthens. Levels as high as 0.1 g/dL are readily encountered. Some sources state that levels may be as high as 0.2 g/dL.

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Common Misconceptions

One of the most common misconceptions in forensic pathology concerns the ability to specify an exact time of death. There have been numerous cases in which postmortem changes taken out of context confounded PMI estimates. More than anything, environmental conditions alter the decomposition process. One decedent who was preserved in a chest freezer for 1 year showed minimal signs of decomposition. Another individual found in a field in the southeastern United States during summer showed advanced decomposition, yet all investigative information, including a receipt on his possession, indicated that he died within 24 hours of last being seen alive. Interpretation of physical, microscopic, and biochemical postmortem changes without correlation with the circumstances of death may result in significantly erroneous PMI estimates.

Other misconceptions revolve around the presumed ability of the forensic pathologist to definitively differentiate between antemortem injuries and postmortem changes in a body showing significant decomposition. Depending on the degree of decomposition and character of the postmortem artifacts, such differentiation may not be possible. Wounds inflicted immediately before or immediately after death (the "perimortem" interval) are particularly problematic.

Another common myth involves loss of bowel and bladder control at the time of death. Although this may occur, it is in no way a universal phenomenon. In most cases, urine can be recovered from the bladder at the time of autopsy and the rectum often contains fecal material.

Perhaps the greatest misconception revolves around the utility and usefulness of performing an autopsy on a decomposed body. As a general rule, information can be obtained from every autopsy, though putrefaction, skeletonization, or predation may limit the ability of the pathologist to draw definitive conclusions.

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Issues Arising in Court

Issues arising in court concerning postmortem changes may center around postmortem artifacts being interpreted as resulting from antemortem disease or trauma. Indeed, one study revealed that a number of cases were referred for forensic autopsy from lay coroners on the basis of misinterpretation of common postmortem artifacts as antemortem injuries. These changes included purging of fluid, deep bluish lividity, drying of the skin, bloating, and skin slippage.[9]

PMI estimates are often scrutinized in the courtroom and may affect the veracity of a defendant’s alibi. Integration of all gross, biochemical, environmental, circumstantial, and adjunctive information is required before determining a time frame that includes the PMI.

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Contributor Information and Disclosures
Author

S Erin Presnell, MD Professor, Co-Director of Medical and Forensic Autopsy Section, Department of Pathology, Medical University of South Carolina College of Medicine

S Erin Presnell, MD is a member of the following medical societies: Alpha Omega Alpha, American Society for Clinical Pathology, College of American Pathologists, National Association of Medical Examiners, American Academy of Forensic Sciences, International Association of Medical Science Educators

Disclosure: Nothing to disclose.

Chief Editor

J Scott Denton, MD Clinical Assistant Professor of Pathology, University of Illinois College of Medicine at Peoria; Forensic Pathologist and Illinois Coroners’ Physician

J Scott Denton, MD is a member of the following medical societies: Alpha Omega Alpha, American Medical Association, American Medical Association, American Society for Clinical Pathology, College of American Pathologists, Illinois State Medical Society, National Association of Medical Examiners, American Academy of Forensic Sciences, Illinois Society of Pathology, Peoria Medical Society

Disclosure: Nothing to disclose.

Acknowledgements

Stephen J Cina, MD, FCAP Chief Medical Examiner, Cook County; Clinical Professor of Pathology, Rush Medical College of Rush University Medical Center; Clinical Professor of Pathology, Northwestern University, The Feinberg School of Medicine

Stephen J Cina, MD, FCAP is a member of the following medical societies: American Academy of Forensic Sciences, Arthur Purdy Stout Society, College of American Pathologists, and National Association of Medical Examiners

Disclosure: Nothing to disclose.

References
  1. DiMaio VJM, DiMaio D, eds. Forensic Pathology (Practical Aspects of Criminal and Forensic Investigations). 2nd ed. Boca Raton, La: CRC Press, LLC; 2001.

  2. Collins KA, Bennett AT. Persistence of spermatozoa and prostatic acid phosphatase in specimens from deceased individuals during varied postmortem intervals. Am J Forensic Med Pathol. 2001 Sep. 22(3):228-32. [Medline].

  3. Sund-Levander M, Forsberg C, Wahren LK. Normal oral, rectal, tympanic and axillary body temperature in adult men and women: a systematic literature review. Scand J Caring Sci. 2002 Jun. 16(2):122-8. [Medline].

  4. Spitz WU, Spitz DJ, Fisher RS, eds. Spitz and Fisher's Medicolegal Investigation of Death: Guidelines for the Application of Pathology to Crime Investigation. 4th ed. Springfield Ill: Charles C Thomas Publisher, Ltd; 2006.

  5. Campobasso CP, Marchetti D, Introna F, Colonna MF. Postmortem artifacts made by ants and the effect of ant activity on decompositional rates. Am J Forensic Med Pathol. 2009 Mar. 30(1):84-7. [Medline].

  6. Saukko P, Knight B. Knight’s Forensic Pathology. 3rd ed. London, United Kingdom: Oxford University Press, Inc; 2004.

  7. Dettmeyer RB. The role of histopathology in forensic practice: an overview. Forensic Sci Med Pathol. 2014 Sep. 10 (3):401-12. [Medline].

  8. Coe JI. Postmortem chemistry update. Emphasis on forensic application. Am J Forensic Med Pathol. 1993 Jun. 14(2):91-117. [Medline].

  9. Sauvageau A, Racette S. Postmortem changes mistaken for traumatic lesions: a highly prevalent reason for coroner's autopsy request. Am J Forensic Med Pathol. 2008 Jun. 29(2):145-7. [Medline].

  10. Zilg B, Alkass K, Berg S, Druid H. Postmortem identification of hyperglycemia. Forensic Sci Int. 2009 Mar 10. 185(1-3):89-95. [Medline].

 
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The decedent shows persistent rigor mortis with the right arm defying gravity. The body must have been in another position for several hours after death before being placed in a supine position.
Livor mortis on the posterior aspects of the body is caused by settling of the blood because of gravity when the body is in a supine position.
As the postmortem interval lengthens, Tardieu spots develop in areas of lividity, such as this individual's shoulder area, as decomposing capillaries rupture.
Tardieu spots on the abdomen.
Tache noire develops when the eyelids are not completely shut and postmortem drying occurs.
Postmortem purge fluid exudes from the oral and nasal passages; no traumatic injuries were uncovered at autopsy.
Decomposition is a process of autolysis and putrefaction.
Maceration after retention of an intrauterine fetal death.
Rigor mortis of the erector pilae can result in postmortem "goose flesh."
Pressure on unfixed livor results in blanching of the coloration.
Livor mortis in an anterior position. The area of blanching across the chest and abdomen resulted from the decedent lying on top of his left arm and right hand.
The lung is dark purple in the posterior dependent areas as a result of livor mortis. This may simulate congestion.
Decomposition has progressed in this individual with breakdown of blood vessels and extravasation of red blood cells into the subcutaneous and adipose tissues of the abdomen, simulating antemortem hemorrhage. There were no associated cutaneous or bony injuries, and the scene was innocuous.
Postmortem drying of the tongue and mucosal membranes darkens the tissues, imparting a pseudohemorrhagic appearance.
Early decompositional changes are manifested by green discoloration over the abdomen.
Marbling outlines the vasculature in this decedent as the postmortem interval lengthens.
Decomposition advances with green discoloration of the skin, generalized bloating (beginning in the abdomen), and vesicle formation with subsequent skin slippage.
Postmortem degloving of the hand.
A law enforcement official utilizes the degloved fingers to obtain fingerprints.
View of collapsed, decomposing organs in the chest cavity with maggots present and gaseous distention of the intestines.
Liquefied fat draining into the chest cavity.
Mummification of this homicide victim occurred after she remained in a secure bedroom in August in the southeastern United States for almost 2 weeks with no air conditioner. Mummification preserved the numerous stab wounds and incised wounds, allowing accurate postmortem assessment of her injuries.
Adipocere has developed in this person who was sealed in a barrel containing water and buried for over 5 years.
Although waxy, the internal organs resist putrefaction when converted to adipocere.
Isolated mummification may be evident in areas of the body with less tissue mass, such as the nose, ears, hands, and feet.
The decedent demonstrates almost complete skeletonization of the head as a result of maggot activity.
Fly eggs, which resemble Parmesan cheese, accumulate on moist areas and accessible orifices of the body.
Young maggots resemble fly eggs but are mobile. In this case, fly eggs were laid in the moist environments of the partially open eyes, nares, and mouth. The eggs hatched and migrated across the face.
Fly pupae such as these are often recovered away from the body, because maggots migrate before pupation; these should be recovered from the death scene if the time of death is in question.
Fly pupae on a decedent; note the presence of other insects.
Postmortem ant and roach activity leaves a typical grouped pattern of postmortem "abrasions."
This individual was recovered in a home with rats. Postmortem bite marks are yellow, bloodless defects with scalloped edges. Top: Third metacarpal and proximal phalanx. Bottom: Fifth metacarpal and proximal phalanx.
Postmortem gnaw marks on a long bone.
Postmortem vulture activity on the leg of a woman recovered in a wooded area; the underlying tendon is exposed, and much of the musculature is absent. Irregular, yellow defects around the deeper wound are consistent with beak marks.
Postmortem tissue consumption caused by small marine animals such as fish and crabs on the dorsal hand. The edges of the defects are typically scalloped.
Larger marine life such as sharks and alligators may consume large amounts of tissue and leave sharp injuries in the soft tissue and/or bone. In such cases, it may be difficult to determine whether the injuries represent antemortem trauma or postmortem artifacts.
This skeleton is that of an adult man who had been missing for 1.5 months during the late fall in the southeastern United States. He was found in a wooded area. Although the skeleton was mostly intact, gnaw marks were evident on several ribs.
Congealing of subcutaneous adipose tissue on the neck of an infant may mimic trauma.
Trochar hole in an embalmed decedent (button removed).
Fungal growth on a previously embalmed and subsequently exhumed body.
 
 
 
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