Algor mortis (Latin: algor—coolness; mortis—of death) is the reduction in body temperature following death. This is generally a steady decline until matching ambient temperature, although external factors can have a significant influence.
A measured rectal temperature can give some indication of the time of death. Although the heat conduction which leads to body cooling follows an exponential decay curve, it can be approximated as a linear process: 2° Celsius during the first hour and 1° Celsius per hour until the body nears ambient temperature.
The Glaister equation, for example, is (98.4°F − rectal temperature) / 1.5, giving hours elapsed since death.
As decomposition occurs the internal body temperature tends to rise again.