Section 4 -

Post Mortem Changes Mimicking Child Or Elder Abuse Anny Sauvageau Forensic pathologist Montreal, Quebec, Canada

During autopsy, the presence of a traumatic lesion at external exam will alert the anatomo-pathologist of the possibility of a non-natural death. In most jurisdictions, when confronted with the possibility of child or elder abuse, the pathologist will transfer the case to a forensic pathologist. However, those traumatic lesions will sometimes turn out to be normal post-mortem changes. In a recent study in our laboratory, we have clearly shown that post mortem changes mistaken for traumatic lesions are a highly prevalent reason for coroner's autopsy requests. In fact, in this retrospective study, we found that post mortem artifacts misinterpretation occurred in 7,8 % (IC95% 0,05;0,12) of all requested forensic autopsies and in 35,3% (IC95% 0,23;0,50) of autopsy cases with significant signs of decomposition. These misinterpretation were based on 5 categories of post mortem changes: purge fluid drainage (66,7%), bluish discoloration by lividity (27,8%), parchment like drying of the skin (22,2%), bloating from gas formation (22,2%) and skin slippage (5,6%). Therefore, it is important to be familiar with post mortem changes and to be aware of the possible misinterpretation as traumatic lesions. We here present the 4 main categories of post mortem changes: lividity, rigidity, change in body temperature, and decomposition. I – Lividity Lividity, or livor mortis, or livor mortis (Also sometimes called post mortem hypostasis), is a dark purple discoloration of the skin that appears progressively in the hours following death. This discoloration should not be confused with ecchymosis or hematomas. In a living person, the heart beats and maintains the flow of blood inside the blood vessels. After death however, the cardiac pump stops and gravity causes the blood to pool in the lower parts of the body. This blood redistribution, which produces a bluish-red discoloration of the skin in the dependant portions of the body, generally appears around 30 minutes after cardiac arrest and progressively increases until maximum discoloration around 2 hours after death. Nonetheless, this time frame is approximate since several factors may modify the development time of lividity. Tissue compression on pressure or support points will prevent the formation of lividity by interfering with capillary congestive distension. If the body is moved shortly after death, blood will redistribute under gravity to the new lower body parts. On the other hand, if the body is moved after more than 8 to 12 hours after death, decomposition of vessel walls allows red blood cell and hemoglobin leakage into the surrounding tissues with lividity fixation: from this moment on, body position change will not be associated with a positional readjustment of lividity. Although lividity can be used in the establishment of time of death, this post mortem change is even better at demonstrating the position of the body at death. Lividity will also indicate if the body has been moved afterwards. Since lividity is secondary to blood gravitational pooling in the dependant body parts, this type of post mortem change is very subtle or even unapparent in cases of important blood loss or severe anemia. On the other hand, lividity can be a bright cherry red color instead of a dark purple in cases of carbon monoxide intoxication, cyanide intoxication and hypothermia. A particular form of lividity, called Tardieu spots, is often confused with petechiae or purpura. Tardieu spots are small bluish lesions formed by blood vessel rupture in areas of important post mortem congestion. II – Rigidity Rigidity, or rigor mortis, refers to progressive muscle contraction secondary to ATP (adenosine triphosphate) depletion. [During muscular contraction, conversely to what is often thought, it is not the myosin head attachment to actin that requires ATP energy but the myosin head detachment.] Rigidity generally becomes apparent between 2 to 4 hours after death and increases progressively to a maximum level around 6 to 12 hours. However, this time frame is only an approximation since several factors can accelerate or decelerate the development of rigidity (ambient temperature, sun exposition, wind or air draught, clothing, intense ante mortem physical activity, ante mortem convulsions, ante mortem fever…). An extreme example of the very quick appearance of rigidity is a cadaveric spasm: this is an almost spontaneous state of rigidity at death, secondary to an increased ATP consumption just before death by particularly intense physical exercise. Even though rigidity develops at the same rate in all body muscles, it is first noticeable in the small muscles and extends progressively throughout the body. Generally, rigidity appears first in the jaw muscles, followed by the upper limbs and then the lower limbs at last. Goose bumps are a particular form of rigidity that is secondary to the contraction of the piloerector muscles, which lift up body hair. Presence of goose bumps on a dead body is meaningless. It must not be thought of as a sign that the victim was cold or fearful before his death. With the onset of body decomposition, actin and myosin linkages in muscle are released and the body loses its rigidity. Rigidity usually disappears between 24 to 36 hours after death. Rigidity, like lividity, is helpful not only for the establishment of time of death, but also for demonstrating that a body has been moved. III – Change of the body temperature In living human beings, body temperature is maintained between 36,7°C and 37,2 °C. Following death, the body's mechanisms can no longer keep the internal body temperature within this range. As a result, the internal body temperature gradually deviates away from its set range, towards the temperature of the surrounding environment. This is a process known as algor mortis. In Quebec, the ambient temperature is almost always less than 37°C, so the body gradually cools after death. Meanwhile, in warmer climates such as the deserts of Arizona or California, the external temperature has the opposite effect: the body temperature gradually increases following death. IV – Decomposition Decomposition of the body is caused in part by putrefaction induced by bacteria and in part by enzymatic autolysis. One of the first signs of decomposition, which appears approximately 24 hours after death, is the appearance of a greenish discoloration, generally in the lower right quadrant of the abdomen. This discoloration is caused by putrefaction and the proliferation of bacteria, and should not be confused with ecchymosis or hematomas. In the days following death, this greenish discoloration progressively extends over the rest of the body. Another post-mortem change involved in decomposition is the appearance of a spot known as a tache noire. The tache noire reflects the drying of the conjunctivae of the eyes wherever they are exposed to air, and is often confused with conjunctive hemorrhage. Approximately 36 to 48 hours after death, blood vessels become apparent through the skin: this is known as marbling. This phenomenon is explained by the presence of sulfahemoglobin, which is formed when decomposing hemoglobin reacts with hydrogen sulphide in the dilated subcutaneous blood vessels. Decomposition also causes the gradual formation of autolysis fluid, or purge fluid, which escapes from the body through the nose and mouth. This fluid is often incorrectly assumed to be blood, which raises the suspicion of head trauma. Purge fluid does build up inside of body cavities and it should not be mistaken for hemothorax or hemoperitoneum. Autolysis fluid also accumulates between the epidermis and the dermis, which makes the skin slippery. As a result, the epidermis gradually detaches from the dermis and slips off of the body, bringing hair and nails along with it. The body will also become bloated, due to gases that accumulate when bacterial fermentation occurs. Bloating observed in body tissues should not be confused with swelling in a traumatic context. Additionally, bacterial fermentation produces alcohol, so the blood alcohol level of a decomposed body has little, if any, value. Special Forms of Decomposition There are two special forms of decomposition: Mummification Adipocere These distinct forms of decomposition occur only when the body is found in a particular environment. Mummification involves the intense dehydration of the body and its tissues, and is observed when the body has been left in a dry, hot environment. Adipocere, on the other hand, develops when the body is left in a humid environment, and involves the hydrolysis and hydrogenation of body fats. As a result, flesh becomes yellowish-white and gives off a strong rancid odor. References Sauvageau A, Racette S. Postmortem changes mistaken for traumatic lesions: a highly prevalent reason for coroner's autopsy request. Presented at the European Academy of Forensic Science, Helskinki, June 2006. DiMaio VJ, DiMaio D. Time of death. In: Geberth VJ, series editor. Forensic pathology. 2nd ed. Boca Raton, FL: CRC Press; 2001:21-41. Perper JA. Time of death and changes after death – Part I:Anatomical considerations. In: Spitz WU, ed. Spitz and Fisher's medicolegal investigation of death, 4th ed. Springfield: IL: Charles C Thomas; 2006:87-127.