How Can Evidence Be Used to Estimate Time of Death?

By the end of this lesson you will be able to: a)Define the factors that scientists use to establish time of death b)Compare and contrast the factors that scientists use to establish time of death c)Calculate time of death using information gathered from a crime report

Lividity: the draining of blood into the lower portions of the body due to gravity Also known as ‘livor mortis’ or hypostasis What to expect: A. Within 1-2 hours: patchy discoloration B. Process is complete within 6-12 hours

Rigor mortis: Stiffness that occurs in body joints after death Cause: The build-up of waste in the body due to the failure of certain biological processes

Algor mortis: The reduction in body temperature following death Body temperature is typically around 37 degrees C AVERAGE DECREASE IN BODY TEMPERATURE A o C per hour for the first 12 hours B o C per hour after 12 hours until body reaches temperature of the environment (within 24 hours)

A.Clothing: Clothing insulates the body; heavy clothing will slow the speed of cooling B.Air Temperature: A body will cool faster on a cold winter night than on a warm summer night

C. Body Fat: Fat tends to insulate the body; the more fat a person has, the slower the body cools after death D. Water: A body in water cools much faster than one in air

Stomach contents: A.It takes about 2 hours for foods like pizza to digest in the stomach B.It can take anywhere from 22 hours to two days to complete the absorption of food into the body

FALSE SENSE OF SECURITY Stomach contents can be used to prove if the deceased was perhaps lured into a false sense of security by their assailant by having a meal with them. A good example of this would be if the deceased's stomach contents consisted of some sort of pizza. The pizza would take roughly two hours to digest within the stomach. If the autopsy was performed and showed that the pizza was still in the stomach then it would be safe to assume the deceased died within two hours prior to discovery.

Stomach contents can also reveal if the deceased was possibly experimenting with any form of drug or exotic food, which might bring about a state of internal poisoning. As a generally accepted rule stomach contents are analyzed for trace elements of poisons or other toxins that might not normally be found in the deceased's system. This is useful if there is a suspicion of drug abuse or poisoning.

Appearance of eyes: Within 3 hours of death, a thin cloudy film develops over the eye and the eyeball becomes softer due to less fluid pressure Skin color: After 48 hours after the time of death, bacteria begins to breed on the skin, giving the skin a greenish tone, starting in the stomach area. After about 4- days, the skin will take on a marble appearance as veins approach the skin surface

Entomology: only certain insects will feed and lay eggs in environments where decomposition is taking place HOW ENTOMOLOGY WORKS Their larvae cycles and development can determine whether a body has been dead for just one day or up to 4 weeks

Cell phone ATM records Eyewitness accounts

1-2 hours: ………Early signs of lividity. 2-5 hours: ………Clear signs of lividity throughout body. 5-7 hours: ………Rigor mortis begins in face hours: …….Rigor mortis established throughout the body, extending to arms and legs 12 hours: ……….Body has cooled to about 25°C/about 78 0 C internally hours: …..Body has cooled to surrounding temperature. 24 hours: ……….Rigor mortis begins to disappear from the body in roughly the same order as it appeared. 36 hours: ……….Rigor mortis has completely disappeared. 48 hours: ……….Body discoloration shows that decomposition is beginning.

Within the Last 3 Hours Lividity Rigor mortis Stomach contents Algor Mortis Appearance of eyes Within the Last 3 Days Skin Color Entomology