As we all know after death body temperature drops. Whereas the average body temperature is about 37 degrees Celsius (98.6 degrees Fahrenheit), after death this temperature drops at a fairly steady rate.

After death the body temperature of a person will begin to drop. At room temperature a dead body will lose heat at a rate of about 1.5 degrees Celsius in the first hour after death, and between 1.5 and 1 degrees for every hour after that. This useful method can to used to pinpoint the time of death. However there are factors that affect this rate, and these are not just situation factors. If the victim died due to asphyxiation or cerebral haemorrhage, the initial body temperature may be higher than usual. Aslo, a naked body will lose heat faster than a clothed body. Usually, larger people lose heat slower than smaller people.

The situation of the body and the environment also has an affect. If the body has been in water the body temperature will cool down much quicker, whereas if the body is in the middle of the desert it would lose heat much slower and may have a higher temperature to start with. Forensic scientists have to take all of these factors into account.

The general formula used for working out the time of death is: normal body temperature divided by 1.5 = number of hours since death.

Decomposition also takes place after death. This is the breaking down of body tissues, which can also be affected by the environment. Rigor Mortis is one of the best know changes post mortem, but it is very unreliable. Rigor Mortis is the stiffening of the muscles, caused by the accumulation of certain salts in the muscle fibre. This kicks in about 12 hours after death, and takes another 12 hours to disappear. This can help in the pinpointing of time of death, but it is unreliable.

The rate of decomposition can also be affected by the humidity of the location. If the body is in a damp environment it will decompose quicker, whereas a dry environment slows down the rate of decomposition.