THE’forensic entomology It is one of the applied sciences that provide a Essential contribution to investigations concerning murders: the presence of certain insects on a corpse, for example, proves to be essential to calculate thepost mortem interval (SMEs), i.e. the time spent from the death, but also to reconstruct the facts and evaluate whether the murder occurred at the place of discovery of the corpse or from another side. We see representations on TV: in the series CSI – Crime scenefor example, there is a forensic entomologist who takes insect larvae From corpses found in a forest or examines them in the laboratory under the microscope, obtaining fundamental information on the crime. It is a discipline now consolidated in the USAbut also in Italy it is taking hold, even the judiciary during investigations does not yet systematically support.
Which insects are witnesses of a crime?
A corpse can represent one number of organisms for a large number of organisms source of nourishment, a refuge or a suitable place for reproduction and that is why over 400 species of insects, In addition to various other arthropods they can colonize a body in subsequent moments and in various phases of the decomposition. For this reason they are sometimes called “death workers”. The type of colonization varies with the passage of time, but is also influenced by the season, by temperature and from the nature of the place. The fauna that colonizes a corpse in the city or in a closed environment differs, at least in part, from what can attack it in a forest, on a beach or even in water. It is precisely these factors that contribute to defining the details of the “crime scene”. From the early hours after death onwards There are groups of insects with different roles And through a careful study of this succession the interval can be reconstructed post mortem.
For great lines and in experimental conditions, here is the succession:
- within the first 18-30 hours From death: colonization takes place mainly by the companies of the Calliforidi and Muscidi families. The blue mosconi of the meat appear (Calliphora Vomitoria) and the green flies (Sericata) attracted by volatile substances produced by bacterial strains that have started the chemical processes of the decomposition.
- starting at approximately from the 4th day In summer, longer in winter: the penetrating smell also attracts sarcophagids, in particular the carnary fly (Sarcophaga Carnaria). These and other ditters lay eggs from which larvae develop. The degree of development of the larva can allow the calculation of the death date with a precision of a day or not.
- Starting from the 8th – 10th day: Several families of beetles begin to appear and among them the silphide and the demestides, or “dermis eaters“, attracted by now dry organic material.
It must be said that, based on the characteristics of the environment such as temperature, humidity, exposure to external agents, The timing can be very variable. To the insects so called cadaveric can also be applied Toxicological investigations To identify the possible presence of drugs or toxic substances on the fabrics. For example, ditto larvae that feed on decomposition fabrics can bio-accumulating any drugs or drugs used by the subject before dying.
A secular collaboration and meticulous collection methods
The first case documented on the use of insects in judicial investigations dates back to about the mid -1200. It is said that in China a murder case in a rural area was resolved by observing the flies that had laid on the bonnet of the construction: they had been attracted by the smell of traces of blood remained on the tool that the killer had used to hit his victim. Instead, the first scientific treaty of forensic entomology was written around the mid -1800s in France by the scholar JP Mégnin who began to study and describe the so -called “cadaveric fauna”.
The entomologist arrives at the crime scene with masksuit, latex gloves and with a series of equipment (entomological tweezers, brushes, test tubes and hermetic containers). It must be thoroughly inspected not only the corpse, but also the whole surrounding environment And a series of environmental parameters must be measured, such as the temperature, the humidity of the room or the presence of obstacles that may have delayed the colonization of insects. All the insects found above, below and in the corpse or in the immediately surrounding area must be carefully collected, preserved and analyzed by an expert entomologist. Sometimes it is also necessary take eggs and larvae alive to be raised in the laboratory for a correct identification.
