On the Scale of the Forensic Entomologist

Forensic entomologists can be involved in the search process and participate actively in it. When the site is accessible, observation of soil compaction can be done. But when time has elapsed, such compaction is not so easy to discriminate.

At shallow depth, decomposition of organic matter produces decaying fluids. They impregnate the soil and provide rich nutrients sought by roots of plants (Rodriguez and Bass 1985). That is why difference of growth of plant and contrast of colour can be observed above the grave. These authors added that changes of foliage, due to previous burial, are signs of potential digging. In contrast, a deep grave modifies the layer of soil disposition and also does not permit roots to reach the soil imbibed of rich nutrients because of the digging. Such a situation generates retardation of surface plant growth (Rodriguez and Bass 1985) and creates an artificial but visible difference in the vegetation aspect. Moreover, disturbance to the soil is shortly linked to the importance of digging but also reduces the above-grave vegetation development. Such observations can be good indicators for forensic investigators (including forensic entomologists) to locate a burial site.

Rodriguez and Bass (1985) proposed to use methods employed by archaeologists to locate buried sites and funeral pits by inserting probes (pH, soil conductivity, temperature) into the soil of expected graves and observing changes in comparison to natural soil (experiments performed between 0.3 to 1.2 m). However, such methods require to have already defined a site with potential graves and do not apply to large perimeters. At shallow depth, the presence of flies flying and landing on soils may also indicate the presence of decaying organic matter.

The Forensic Entomology Department (IRCGN, France) has initiated since 2008 cooperation with the cadaver dog and handlers' investigation team specialised in cadaver search (CNICG - France) and the Signal, Images and Voices Processing Unit (IRCGN) investigating in the same field with GPR. Usually, the local forensic pathologist and local crime scene technicians (CST) are involved in such recovery operations. The aim of this approach is to propose to investigators and magistrates a complementary experts team from the location of a corpse until the sampling operation. When a search of cadaver operation is known and planned, each team can alert one another (CNICG is located 600 km from IRCGN) and can in this way be available in a short duration. Experience shown that investigators focus on identification elements and evidence that could provide information on the cause of death (gun, bullet, knife, string, bone element, etc.) which may be forgotten. The presence of a forensic entomologist within the team decreases the risk of forgetting insect collection. For instance, such an approach may provide promising results and satisfy the different personnel involved (judge, investigators, CST, etc.).

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