Forensic entomology has long been used to aid legal investigations by depicting insect behaviour. The most common practice applied is the determination of Post-Mortem Interval (PMI). PMI is the time elapsed since death.

Blowflies and beetles have a particular period for each of their life stages, ranging from eggs to maggot to pupa and finally adult. Each life stage has a known time period, though depending on the species, with a ±1-3 day difference.

If maggots are to be found feeding on a corpse, the oldest maggots present on the corpse can be used to provide PMI estimation. The size (length) of the maggots will be used to determine their age. The age of the oldest maggot would reflect the PMI for the corpse and, in return, determine the estimated time of death.

In cases where the corpse is severely decomposed and the medical examiner is not able to log the corpse body temperature to determine the time of death, the use of insects can serve as a suitable alternative for this purpose.

Blowflies, specifically, are the most dominant species to be used in this field due to their reliability in arriving at the scene within the first few minutes. They would come to feed and lay their eggs. They can fly from a high-rise building to dwellings, and they have a short ±14-day lifecycle whereas other insects can take up to between two and nine months to morph from egg to adult.

Detecting presence of drugs or toxins

Besides PMI determination, insects feeding on the corpse can also be used to detect the presence of drugs or toxins that the person had consumed before death (ante-mortem). When the corpse has no or little biological sample available for toxicological analysis, the maggots or insects that feed on the intoxicated tissue can be used to determine the type of medication or toxins that the person had ingested ante-mortem as the cause of death. Insects have a higher level of toxin threshold than humans, thus they are able to withstand a human lethal dose. And they are also able to retain the toxin in their system throughout the maggot phase to an adult.

It doesn’t stop here. Insects can also provide information on the post-mortem movement of the person based on the species of insects feeding on the corpse.

Blowflies and beetles contribute best in this area. These two species are very distinctive to a particular choice of feeding, humidity and habitat. Just like flesh-eating flies, house flies and fruit flies have their own particular feeding preferences.

For example, the presence of cluster flies feeding on the wounds on a corpse that was found buried for a week. The corpse, upon excavation, would have indicated that the murder might have taken place in an inhabited dry space which cluster flies favour as cluster flies are not normally present in the dark and humid environment deep in the soil. The presence of cluster flies helps to narrow down the search for the crime scene. To elaborate, other factors will have to be considered by the entomologist, such as the insect species, insect access to the corpse post mortem, surrounding temperature and humidity level.

Stored product entomology

Forensic entomology is not only confined to criminal investigations but also expands to urban and stored product entomology. Urban entomology deals with insects that could compromise human habitation and environment such as destructive pests (bees, bed bugs and mites) and mosquitoes as vectors for malaria and dengue. The cases would usually involve between private home-owners, the pest control company and the property tenant.

Stored product entomology, however, evolves around pests infesting processed food, commodities and agricultural products for sale. This usually involves food manufacturers due to the processing technique and improper storage of the goods by the manufacturer or seller. Stored product entomology cases, however, can be escalated to criminal investigations if it involves monetary damages and insect-infested crops that lead to injury or death of an individual.

Forensic entomology lends an intriguing scope to the use of insects for legal purposes. Experts in this field are typically attached to research institutes and universities. Their presence can be requested by the police and pathologists should they need them to cooperate in the investigation for sample collection and sharing their expert opinion in court.

This humble and yet enticing field is still full of possible discoveries. In the new era where alternatives are favoured over the previous complacent ways to fit the new norm, let us explore more on the potential of our natural surroundings to create more sustainable methods for our future.

-- BERNAMA

Reena Abd Rashid is a lecturer with the School of Chemistry and Environment, Faculty of Applied Sciences, at Universiti Teknologi MARA, Shah Alam.