Entomology is the study of insects, and forensic entomologists use insects to provide more information about crimes.
The first record of the use of forensic entomology is Song Ci (sometimes called Sung Tz’u), a lawyer in 13th century China.
The live and dead insects found at the site of a crime can tell the forensic entomologist many things, including when and where crimes took place, whether the victim had been given drugs, and in murder cases, the time since death, and the length of time the body had been there.
When and Where
Some insects are only found in specific areas, so finding these at a crime scene can help find out where the crime took place – for example finding insects that are most common near water on body that is found inland could suggest that the body has been moved.
Some insects are only active at night, or during the day, so finding these could support evidence of when a crime took place. For example, a suspect may claim to only have driven during the day, but evidence of night-flying insects on the suspect’s car would go against this.
By analysing the bodies, shed skins or faeces of flesh-eating insects found at a crime scene (entomotoxicology), forensic entomologists may be able to determine whether drugs were used, and which they were.
Forensic scientists can extract the DNA from blood consumed by blood-sucking insects. This can be used to place someone at the scene of a crime, supported by evidence of bite marks.
Insects In Murder Cases
Some insects scavenge dead flesh or lay eggs in dead bodies. Forensic entomologists study the kinds of insects found in and near bodies, and by knowing the life cycles of the different insects, and the stages of decomposition when different insects populate dead bodies, can determine the time since death (post-mortem interval) or the length of time the body has been there, if it has been moved since death.
The first insects on bodies are usually flies, including houseflies. Different flies arrive at different stages – some are attracted to newly dead bodies, others will only arrive three to six months after death. Beetles tend to arrive as the body decomposes.
The succession of flies and the length of their life cycles will depend on the location, time of year, weather, and whether the body was on the surface or buried.
Some bees and wasps predate flies and their larvae, and can cause difficulties by removing the insects used by forensic entomologists to study the crime scene.
Insects In Abuse Cases
Insects can be used as evidence in human and animal abuse and neglect cases – for example, flies can lay eggs in untreated wounds, and flies will be attracted to unchanged nappies or incontinence pads in neglected babies and elderly or disabled people.
Insects can walk through bloodstains and leave bloodstained droppings at crime scenes, which can cause confusion.
Insects and insect bodies can help identify the country of origin of illegally imported vegetable matter, such as cannabis.
Bee and wasp stings can cause car accidents, and the police may call in forensic entomologists to confirm this as a cause.