According to Newton’s law of cooling, exchange of heat occurs from warmer object to colder objects until both objects are at an equilibrium of temperature. Cooling of dead body also follows the same principle but with less uniformity.
Since human body is not a uniform structure, its temperature will not fall evenly. Each body part has its own unique environment due to which there is variation in axillary, oral and rectal temperatures even when taken at the same time. Also, each body will lie in its own unique environment and each body will cool at a different speed, depending upon the many factors affecting it. Estimation of time since death based on body temperature can again be used only as an assumption.
Some important factor effecting the cooling of body after death
- Posture of the body: extended or curled into a fetal position
- Clothing: type of material, position on the body – or lack of it
- Obesity : fat is a good insulator and emaciation :lack of muscle bulk allows a body to cool faster
- Environmental temperature: day, night, winds, rain, humidity, mass of the body, surface area
- Body temperature at the time of death, site of reading of body temperature