Postmortem interval helps determine the time of death in homicide investigations. Pathologists use indicators such as insect activity and rigor mortis to calculate the interval, but environmental factors and clothing can affect accuracy. It is useful in investigating suspicious deaths.
A postmortem interval is the time that elapsed between the time a person dies and the time the body is examined. Commonly used in homicide investigations, knowing the post-mortem interval is helpful in pinpointing the time the person died. Ways pathologists can calculate postmortem interval include identifying the species of insects that live in the body, how quickly the person’s body has decomposed, and other indicators such as the presence of rigor mortis.
Through studies and research over the years, pathologists have been able to develop reference charts for the rate of decomposition of the body after death. An example is rigor mortis, which refers to the temporary stiffening of the body that occurs for some time after death. If a deceased person is not in rigor mortis, they are in the very early stages of decomposition or have passed the stage of rigor mortis. Typically, determining a postmortem interval involves taking several signs into account.
Rigor mortis, for example, can be assessed in conjunction with a person’s core body temperature, commonly of the liver. Because cooling occurs after death, a residual temperature, along with rigor mortis, can give a coroner a relatively accurate idea of the postmortem interval, and thus the time of death. Another important indicator of time since death is insect activity on the body, useful after rigor mortis has passed. The stages of the insect life cycle, from eggs to larvae to adults, can help pinpoint when insects first colonized the body.
However, these reference standards are not always accurate, as there are many confounding variables in the field of pathology. The environment that a person’s body is a part of can vary widely in factors such as temperature, humidity, and the presence of water. In addition to the natural characteristics of the body’s position, man-made factors such as the type of clothing the person wears can also influence the rate of decomposition and interfere with the interpretation of the postmortem interval.
Determining the post-mortem interval is very useful for investigating suspicious deaths. It can help investigators figure out when the person was last seen, figure out what happened in the moment immediately leading up to their death, and vindicate or implicate other people in the death. Typically, identifying the postmortem interval is not useful information for the postmortem examination of people who died under unsuspecting circumstances.
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