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Fly, homicides and cadavers – MediNick

By CoperNick

 Alice Gaggero

 

March 25, 2020

Today I am going to introduce you to a different way of studying a crime scene and solve criminal cases:  forensic entomology, in other words studying the insects present on the crime scene and on the cadavers to help solve the case.

This seems incredible, but the reason why it could be an effective method is that, once an individual is dead, the body will be colonized by various insects and their larvae, which leave their shells behind them.

Entomology dates back to the 13th century, when, following a case of homicide in Asia, flies indicated the murder weapon’s place.  In Europe the practice only began about two centuries ago thanks to the work of Bergeret. However, forensic entomology was first applied in 19th century, when a French couple was acquitted for the death of an infant, whose mummified remains and associated fauna were discovered behind the mantlepiece in their home.

Entomologists have divided the insects in four categories based on their features:

– Necrophages, that are the species feeding on body’s tissue; the determination of the age of these insects is usually the base for making the estimation of the time of death.

 

 

Figure 1: Example of Necrophages

 

– Omnivores, are species that feed themselves with both the body tissue and associated fauna; these insects could retard the rate of body’s composition, because they can decimate the population of necrophages.

 

 

Figure 2: Example of Omnivores

 

– Parasites and Predators, as the name suggests, are parasites and predators of both humans and other insect species.

 

 

Figure 3: Example of Parasites and Predators

 

–  Incidentals, are insects that use the corpse as a concentrated resource extension of their normal habitat.

 

 

Figura 4: Example of Incidentals

 

So the first thing an entomologist could do for the investigation is helping the coroner to establish the time of death grounding on which insects and larvae he found on the body.

In the period immediately after death, the estimation is made based on the time needed by every represented species to grow.

Obviously there are some factors that an entomologist should consider when determining the time of death, like whether the body is found inside or outside, and the kind of weather (like temperature or heavy rain).

Most insects drop off their larvae in a specific season of the year, so, for example, if the individual died in summer it will not be attached by insects that live in winter. This could help if a body is found after some months or more.

This is just one of the many ways entomologists could help the investigations: their help is not useful just in case of homicide, but also of rape or illicit drug use.

Each place has different species inhabiting it. It’s almost like a “fingerprint” of that place: we don’t find the same species in cities or in woods for example, so entomologists could study the different species they see on the body or on a suspect to know if he or she has been in the crime scene or not.

Some species could also be used in case of abuse or neglect of children or old people, like in a recent case in Southern Italy.

(  Follow this link if you want to know more about it: wiki2.benecke.com/images/3/36/Paper_2_bonacci_benecke_case_dead_neglected_man_rjlm_november_2017_283-286_T._Bonacci.pdf)

Some insects like mosquitoes or lice can store some traces of the blood of the human they last bit, giving us an evidence to identify this person, what disease he or she has, or the places he or she has been to. This technique could also be applied to mummies or skeletons if one of these insects is found, for instance, in the hair of the body.

In Italy this technique was used to identify the bodies found on the WW1 battlefields on the Alps.

Today, forensic entomology is more and more often viewed as a proof in the tribunal and is helping to resolve more and more cases.

 

Bibliography:

 

Picture credits:

 

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