Forensic Issues: Determining Time of Death

Determining time of death is important for criminal prosecutions to narrow down the list of suspects. Some things that can aid narrowing down this window are forensic terms you may of heard of: Algor Mortis, Livor Mortis, and Rigor Mortis.

I was fortunate to hear a local coroner speak several months ago. And she reviewed these terms and what they meant.

How fast does a body cool? In a 70 degree room the body will cool 1 degree an hour if maintained at a steady temperature. Issue being, how often are the deceased found in a perfect, unchanging, 70 degree environment? They can be found in temperature extremes, exposed to the elements, or buried in differing depths. All these will effect determining time of death.

Algor Mortis: Reduction in body temperature after death. There is generally a steady decline until is matches the ambient temperature of the environment. Problem being if the body is found in a much hotter area like a house with little air conditioning in a hot, humid environment.

Livor Mortis: Dependent pooling of blood when a person dies. This can be helpful in determining the position of the body at death and if a body has been moved. For instance, let’s say a nude body was found face down, yet their buttocks, heels, shoulder blades and posterior scalp are purplish. This would indicate a change in the position of the body. It starts 30 seconds to two minutes and becomes fixed in 8-12 hours.

Rigor Mortis: Stiffening of the muscles. Starts in small muscle groups first. Begins 2-4 hours, fully developed in 6-12 hours and disappears in 36 hours.

Things that can speed up or slow down these time frames are: the environment, fever, and whether or not the body was buried. Considering the long time frames, an exact time of death is hard and the best hope is to narrow down the time frame.

Here’s a good overview and includes additional discussion of the process of putrefaction.

http://www.deathreference.com/Py-Se/Rigor-Mortis-and-Other-Postmortem-Changes.html

Have you written a scene using any of these concepts?

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