Forensic Entomology: Where Insects Meet the Law

Calliphoridae fly — Flies such as this one, from the family Calliphoridae and collected from a carcass at a New Jersey forensic entomology lab, can provide clues to criminal investigators. (Photo credit: Denise Gemmellaro)

By Denise Gemmellaro

This is the first part in a series of posts on forensic entomology. Stay tuned for future posts in the coming weeks here on Entomology Today.

Thanks to the media exposure it has gained in recent years, the word “forensic” has become a sort of magnet for the curiosity of the general population as well as students in every field. There is, of course, a mystery component in the world of forensics that is both fascinating and intimidating, and it seems like we all love that combination of emotions: a beautiful sunset along a highway rarely slows down traffic the way a graphic car accident does!

Forensic entomology has not been immune to this attention and, thanks to that, it has grown and developed into a strong field of science and has contributed not just to criminal investigations but also to fields such as ecology, evolution, and insect behavior.

Unfortunately, though, while the first documented forensic entomological observations date back to the 13th century, forensic entomology is still a “new” structured discipline, and therefore its practices and scope are being defined more and more every day by the people who conduct research in the field and those who practice it. And through all that time, forensic entomology has been both neglected, misinterpreted, and not properly used for what it actually is.

But what, then, is forensic entomology?

Broadly speaking, forensic entomology is the study of insects applied to any sort of legal issue; as a general formula, one could use insects + law = forensic entomology. That means that every time insects are involved in a situation that requires the intervention of the law, it could be a case where forensic entomology is applied. Following this logic, three general subfields broadly recognized within forensic entomology are stored-product forensic entomology, urban forensic entomology, and the famous (or infamous) medicolegal forensic entomology.

infested rice — When stored products such as rice become infested with insects (or insect larvae), forensic entomologists seek clues from those insects to determine when and where the infestation may have begun. (Photo credit: Denise Gemmellaro)

Stored-product forensic entomology regards insects infesting food products once they have been packaged or after they have been harvested and stored. Examples of this could be moths we find in a rice box stored in our pantry or beetle-infested cereals in a warehouse. In situations like this, it is important to find the source of the infestation to assess some responsibility. Are the moths in our rice found there because we left the package open for too long? Or, is the box completely sealed, meaning the infestation occurred before that package got to our pantry, possibly in the supermarket or, even earlier, when the rice was being packaged? The entomologist, in this case, would be responsible for identifying the insects in question, determining their development stage, and—based on what she knows about the insects’ feeding behavior, typical habitat, and biology—give her opinion on when and how the infestation might have occurred.

When insects such as cockroaches invade structures such as homes, schools, or hospitals, forensic entomologists can work to identify how the infestation occurred. (Photo credit: Denise Gemmellaro)

Urban forensic entomology examines the infestation by unwanted insects of structural environments, such as our homes or, scaling up the problem, a school cafeteria or a hospital. The presence of cockroaches or bed bugs is a typical example of urban forensic entomology cases. The entomologist in this case would be responsible for assessing the level of infestation (Is it one cockroach in the whole apartment? Is it a hundred of them in one room?), identifying the species and the life stage of the insects present on the scene, and providing a potential explanation for their time and mode of infestation. In cases like this, the entomologist is sometimes working with insects that do not pose a real threat to us; consider, for instance, the presence of drain flies in an office bathroom—they will never hurt anyone! However, a perceived threat is more than enough for measures to be taken.

pig with maggots — An array of insect species are necrophagous, meaning they colonize decomposing animal matter, such as this pig carcass at a lab. (Photo credit: Denise Gemmellaro)

Medicolegal forensic entomology is the most well-known subfield of forensic entomology and is about the colonization of decomposing organic matter by necrophagous insects—or, in simple terms, insects feeding on dead matter! These are the maggots eating a dead body that we all love seeing on TV shows. These are the critters that give the chills even to people holding doctorates in entomology, who work with other, less creepy groups. These are the silent informants of many crime scenes who, unfortunately, too often remain silent or speak not too loudly.

In the next post in this series, learn more about medicolegal forensic entomology as we separate fact from fiction regarding what can and can’t be learned from the insects at a crime scene.

Denise Gemmellaro is a graduate student in entomology at Rutgers University and director of the Forensic Entomology Workshop held at the New Jersey School of Conservation, a two-week summer program for students and professionals to gain hands-on experience in the fundamentals of forensic entomology. Email: denise.gemmellaro@rutgers.edu