What Insect Evidence Tells an Investigator
The most commonly understood use of insects evidence is the use of fly larvae to determine the P.M.I. However, by identifying the species of insects and the stage of developmental so much more can be determined.
Urban species in a rural environment or vice versa can indicate that the body has been moved from one setting so another. Similarily the identification of the species can indicate an indoor rather than outdoor death (Anderson, 2000). This does not mean that Blowflies and Fleshflies do not colonize bodies indoors. Some species rarely enter indoor settings and may be absent from the samples obtained. Death indoors, in a vehicle or in water does not stop colonization but does effect the order, family and species of insects which may be recovered (Anderson, 2001)(Erzinclioglu, 2000)(Goff, 2000).
Each type of insect colonizes a body in accordance with its own preference for shade or sunlight, wet or dry conditions, urban or rural and many other environmental conditions. In retrieving these insects an investigator can read the story of where the body has been and for how long.
Skuttle flies colonize buried bodies and may pass through several life cycles underground(Erzinclioglu, 2000).
The presence of Skuttle fly larva on a body found on the surface may indicate a previous burial. Likewise blowfly larvae on a buried body may indicate burial after some time on the surface.
Lack of insect activity can indicate storage at freezing temperatures or enclosure in an air tight container. Sealing a body in a plastic garbage bag, a vehicle, a rug and/or burning it does not deter colonization (Anderson, 2001).
Insects in the soil around a body can be very useful in determining whether the body has decomposed in that location. Over time the normal types of bacteria and insects will be replaced by those associated with decomposition(Goff,2000). By sampling the soil an investigator can determine whether this is a primary or secondary site of death.
Finally, insects not normally associated with bodies may be found in the soil above a buried body. For example, Sphinx moth larvae found in and area central Alberta typically drop from the vegetation on which they feed and burrow into the soil in August and September. If pupa or pupal casings are found in the soil above a buried body then the investigator could conclude that the body was buried before August(from research done by the author fall 2003). Sphinx moth larvae seek out disturbed soil in which to burrow and would be expected to be found in areas of burials for this reason.
Conclusion
There are infinite possibilities for the use of insects in forensic investigations. Every insect tells a story about the conditions the body has passed through and the places it’s been. It is essential that personnel recognize the importance of this evidence. Preservation of evidence can only occur when it is recognized as evidence. Once lost the only witnesses to the processes of death are gone and silent forever.
References
- Anderson G. S. (2001). Insect Succession on Carrion and its Relationship to Determining Time of Death. In Byrd J.H. & Castner J.L. (ed.), Forensic Entomology: The Utility of Arthropods in Legal Investigations (pp.143-175) . Boca Raton , Florida : CRC Press .
- Baden M.M. & Hennesse J. (1989). Unnatural Death: Confessions of a Medical Examiner. Toronto: Random House of Canada.
- Baden M. & Roach M. (2001). Dead Reckoning : The New Science of Catching Killers. New York, N.Y.: Simon & Schuster.
- Bryd J.H. (2001). Laboratory Rearing of Forensic Insects . In Bryd J.H. & Castner J.L. (ed.), Forensic Entomology: The Utility of Arthropods in Legal Investigations (pp. 121-140).: Boca Raton, Florida. CRC Press.
- Erzinclioglu Z.Y. (2000). Maggots, Murder and Men . New York, N.Y.: St. Martin’s Press.
- Goff M.L. (2000). A Fly for the Prosecution. Cambridge, Mass.: Harvard University Press.
- Haskell N.H., Lord W.D. and Bryd J.H. (2001). Collection of Entomological Evidence during Death Investigations. In Byrd J.H. and Castner J.L (ed.) Forensic Entomology: the utility of Athropods in Legal Investigations. (pp. 81 – 120). Boca Raton, Florida : CRC Press.
- Knight B. (19??). Simpson’s Forensic Medicine. (11th ed.): Oxford Uiversity Press.
- Lane B. (1992). The Encylopedia of Forensic Science. London, England: Headline Book Publishing PLC
- Saferstein R. (2004). Criminalistics: An Introduction to Forensic Science. ( 8th ed.). Upper Saddle River, N.J. : Pearson Education Inc..
- Stoerkay M. (2000) Introduction to Forensic Entomology. Retrieved December 1, 2003 from http://folk.uio.no/mstarke/forens_ent/tables_development.html
- Thomas P. (1995). Talking Bones: The Science of Forensic Anthroplogy. New York, N.Y. : Facts on File.
- West I. & Stern C. (1996). Dr. Ian West’s Casebook: the Chilling Investigations of Britain’s Leading Forensic Pathologist. Boston, Mass.: Little & Brown Co.
Quotations
Goff M.L. (2000). A Fly for the Prosecution. (p.43). Cambridge: Harvard University Press
Goff M.L. (2000). A Fly for the Prosecution. (p.43). Cambridge: Harvard University Press
Goff M.L. (2000). A Fly for the Prosecution. (p.45). Cambridge: Harvard University Press
Stoerkay M. (2000) Some Development data on diffent Species of Blowflies(Calliphoridae) and Fleshflies(Sarcophidae) in Introduction to Forensic Entomology retrieved December 1, 2003 from http://folk.uio.no/mostarke/forens_ent/tables_development.html
West I. & Stern C. (1996) Dr. Ian West’s Casebook: The Chilling Investigations of Britain’s leading Forensic Pathologist. (p.231). Boston, Mass. : Little & Brown Co.