How Insects Help in Criminal Investigation

In our previous post, we talked History of Forensic Entomology. In this article, we will get an insight on How Insects Help in Criminal Investigation. Majorly, We get the following information from insects-

1. Estimation of time of death and postmortem interval- Time of death can be estimated by insects by two methods. One is using successional waves of insects (used when the corpse has been dead for between a month up to a year or more) and the other one is using maggot age and development (used when death occurred less than a month prior to discovery).

Case Study-during mid of November in southeastern United states someone called police to investigate a foul-smelling odor which was emanating from a small single-family house.

On investigation a badly decomposed body was found in shallow grave in the basement of the house. A careful examination of the body was done and the soil in and around the body was excavated to look for entomological evidences. Larvae of Calliphoravicina and larvae and pupae of Synthesiomyianudesita was found.

Using information about the developmental cycle of both these species of flies along with supplemental information about the climatic data and soil temperature it was estimated that victim died 28 days prior to the discovery.

2. If the body has been moved or disturbed after death– Sometimes criminal move the dead body from the place of killing to a hiding place. In such situation insects may help in determining if the body is moved or not because some of the insect present on the body may belong to the first habitat (killing place) not the second (hiding place). This may also indicate the type of area where the killing occurred.

3. Presence and position of wounds– On reaching a dead body insect usually starts colonizing in facial orifices first unless there is a wound present. If wounds are present, they will start colonizing first on the wound and then proceed down the body. So, whenever maggot activity is centered away from the natural orifices it may be the site of wound.

Case study- A dead body was found by a man on a trekking trip. It was in such an advanced stage of decomposition that the coroner was not able to determine the cause and manner of death but an investigator present on the scene noticed peculiar pattern of insect invasion on chest and palm.

A forensic entomologist was called and he determined that the insects are attracted to open wounds and the type of wound was consistent with stab wounds to the chest and defensive wounds to the palm of hands.

4. Presence of drugs- In cases when there is not enough flesh left in a dead body to detect presence of drugs, insects are very helpful. Maggots present on the dead body can be analyzed as they bioaccumulate the drugs. The presence of drugs in the dead body can affect the growth and morphology of insects feeding on the dead body.

The fate of drugs in the body of insect depends upon species, development stage, mode of action of drug, absorption, redistribution, and metabolism of drug and drug stability.

For example- drugs like cocaine and heroin can accelerate the larval development and poisons like malathion can delay the insect colonization.

Case study–A dead body of a 22-year-old woman was found along a creek. Near the body was an empty bottle with a prescription label. The body was nearly skeletonized and the soft tissue was gone. Numerous maggots of secondary screwworm were present on the body and were collected for analysis. During the analysis for detection of presence of drugs it was found out that maggots were full of Phenobarbital and it was concluded that the victim committed suicide.

5. Child or senior abuse/neglect- Insects also help in cases of abuse and neglect. Some species of flies are attracted to an incontinent individual; a baby that has not had its diaper changed or an old person who have not been assisted in maintaining their bodily hygiene(the invasion of living tissue with insects is called myiasis). For example- greenbottle Luciliasericata are attracted to odors such as ammonia resulting from urine or faecal contamination.

6. Connect suspect to the crime scene– In very rare cases insects can be helpful in linking a suspect to the crime scene.

Case Study- in Chicago during midsummer, a woman parked her car and was walking towards herapartment, when she was attacked by a man wearing a ski mask. The police began to suspect a man and after getting a warrant they searched his apartment and found a ski mask. The suspect claimed that he had not used it since last winter. Investigator found two cockleburs attached to the ski mask which he sent to the laboratory for examination.

It was found out that within the cocklebur, live weevil larvae were present. Then the cocklebur present on the crime scene was examined and it was revealed that cocklebur present on the crime scene was of the same species as the weevil found on the ski mask. The species was identified as Rhodobaenus 13-punctatus. This species has a life cycle of one year.

Its larvae pupate in cocklebur and emerge in latter part of the summer and then hibernate. It is not possible that it survived the whole winter within a desiccated cocklebur in a heated apartment. This led to the conviction of the suspect.