Forensic entomologists help solve crimes using clues from insects, often involving dead bodies. The first recorded incident where insects were used in a criminal investigation was in 13^th –century China after a farmer was found murdered in a field with a sharp weapon. All of the suspects were told to place their sickles on the ground. Only one sickle attracted blow flies to the trace amount of blood remaining on the tool. Case solved.

Flies Can Pinpoint the Time of Death

Flies are the first insects to get to a dead body. A female blow fly can detect and lay her eggs on a dead animal or person less than an hour after death. The flesh fly doesn’t even take the time to lay eggs, but instead deposits live maggots on the body. Once the fly maggots have fed on the tissues and left the body and as the carcass dries, carrion beetles may appear. Dermestid beetles show up once most of the soft tissue has been consumed to feed on dried tissue and hair.

Forensic entomologists use their knowledge of the biology and habits of these insects to help pinpoint the time, location, and sometimes even the cause of death. The types of insects present and the fact that different insects prefer their carcasses to be of a certain age allows experts to predict when the victim died. Knowing the life cycle of a fly species allows the entomologist to extrapolate just how many days the larval stage would take to develop at the temperatures present at the discovery site. For example if the larvae of a specific blow fly have already pupated, you know that they have been feeding on the body, given the temperature, for at least 7 days. Add to that 1 day for the eggs to hatch and you know time of death was at least 8 days prior.

You Can Move the Body, But Not the Flies!

Sometimes a body is dumped far away from the place of death. By identifying the insects to species and then applying what is known about the geographic range of that species, a forensic entomologist may be able to determine whether the body was moved to the site and where the person actually died.

In one case, a lack of maggots on the body pointed to the real murderer. The victim’s boyfriend reported finding her bloody body in her apartment where she had reportedly been dead for at least one day with windows open. But the lack of insects on the body turned the blame onto the boyfriend who it was discovered had murdered his girlfriend in her air-conditioned apartment with windows closed. The next day he returned to the scene of the crime, opened the windows, and called police. Case solved.

For more on forensic entomology’s role in solving crimes, see these blogs:

• How Insects Solve Crimes
• Forensic Entomology is Not for the Faint-Hearted!