Decay depends on weather conditions in the environment where a body is decomposing. Determining whether the death of a body occurred in the location of its discovery is a factor. In addition, an examination of any physical proof found near the remains, coupled with a forensic evaluation to determine if insect and larvae infestation present in the body include indigenous species found in the area.
Once forensic analyses have determined the approximate location where death occurred and identified past weather conditions in the area and the types and arrival sequence of insect infestation present in the body, any other external evidence uncovered by investigators can be factored together to produce a roughly precise time of death.
Strewn about a three-acre farm in Knoxville, Tennessee affiliated with the nearby state's university are human remains scattered in various stages of decomposition. The cadavers range in age from mid-teens to a century or more at the time of their deaths. Students and law enforcement from around the United States and abroad have utilized "The Body Farm" since 1971 to promote the science of human post-mortem decomposition and the factors which influence it.
Many factors determine how long a human body will take to decompose. Things like temperature, humidity, size of the person, bacteria available, and amount of fat as opposed to muscle will affect the length of decomposition. Whether a body is embalmed, if it is above ground or buried, contained in a coffin, or other container are also factors. Typically, a human unburied body with no added chemicals can be decomposed to bones in eight to twelve days. A buried body can retain tissue for a year, and an embalmed body can stay intact for many years.