Techniques

Estimating Time of Death (TOD)

Coroner measures temperature of liver to determine time of death.

Medical investigators look for various signs to help them estimate a time frame - usually a two to four-hour window of time - in which the victim probably died. These signs may include the following:

• Rigor mortis
  (the stiffening of the muscles that occurs shortly after death)
• Lividity (pooling of blood)
• Body core temperature
• Clouding of the corneas
• Evidence of a decompositional process
• Presence/absence of purge fluid
• Drying of the tissues.

The organs most commonly used to determine the body core temperature are the liver and the brain, because of their mass and density. After death, the body temperature falls toward the temperature of the surroundings at a rate of about one-and-a-half degrees per hour. This rate will vary depending on the amount of body fat, the amount of blood loss, the amount of type of clothing worn by the victim, the location of the body (whether it was lying near a heating or air conditioning vent or inside a cooler), and, if the body was found outdoors, on the weather conditions, including air temperature, wind, and precipitation (rain or snow).

Diagram showing how liver temperature, relative to room temperature, determines time of death. Since the temperature of a dead body falls at about one-and-a half degrees per hour, the 87 degree liver temperature indicates death at 6-7 hours before.

For other techniques used in Forensic Files, click here.

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