blog pai poenja

If only death people could talk,,

Posted in Forensic Entomology & DNA Barcoding by paibiopai on December 15, 2009

“The body and the decomposers are telling you what happened, If you can only understand the language.”

-Lord and Rodriguez (1989)

Since the inception of human species, man has tried to dominate this planet by sheer intelligence. This dominance led to the concept of noosphere and he started interfering with natural processes. But nature has her own ways and one of its finest intricacies is the food web i.e. the process of eating and being eaten. This cycle is so immaculate that even dead bodies of animals, including that of humans, are decomposed by other creatures with insects playing a predominant role. And who knew that one day these so called natural scavengers would act as witness to man’s mud-paddling strategies for personal ambitions, jealousy and gains. Practical use of these organisms in solving crime led to the development of a separate branch of science now-a-days known as Forensic Entomology.

This science emerged as a major discipline with passage of time in the developed countries and its role in criminal investigations became more and more relevant. Forensic entomology proceeds on the common observation that exposed remains present a temporary and progressively changing habitat and food source for a wide variety of organisms ranging from microbes like bacteria and fungi to vertebrate scavengers. Out of these, arthropod fauna comprises a major element of the biota and insects form the most constant, diverse and conspicuous group. Cadavers are often fiercely contested by great number of insect species. The overwhelming majority are flies and beetles.

The science of forensic entomology is based on the analysis of those insects which sequentially colonize a corpse as decomposition progresses and on the rate at which the various stages of their progeny develop. This entomological information can be useful during criminal investigations in order to determine the following :

Time of Death : There are two basic approaches to the application of entomological data for estimating the time of death. During earlier stages of decomposition, the time elapsed since death or postmortem interval (PMI) may be determined by calculating the time required for a given species to reach the particular stage of development recovered from the corpse at the time of discovery. The insects involved in this approach are mostly dipterans, especially those belonging to the families Calliphoridae and Sarcophagidae. The most advanced stage of development which in turn shows the longest period of association with the corpse is used to estimate the minimum possible PMI. After the initial stages of decomposition are over and when the Calliphoridae and Sarcophagidae have departed, estimates are generally based on the interpretations of arthropod succession patterns.

Mode of Death : A dead body having external injuries is more attractive to insects than one having none. So, depending upon the degree of degradation brought about by maggots, an entomologist may be able to suggest the possible mode of death, e.g. strangulation or mutilation (Anderson, 1997). Another application is in the cases where death has occurred due to intake of drugs. A chemical analysis of the maggots found on the dead body can reveal the specific drugs, specially helpful when no human tissues are available for sending to the laboratory for other tests. During experimental studies large number  of poisonous chemicals have been recovered from maggots that feed upon animals which died due to intake of such chemicals. To name few, Cocaine (Goff et al., 1989), triazolam, oxazepam, alimemazine, chloripriamine and phenobarbital  (Kintz et al., 1990a and 1990b), methamphetamine (Goff et al., 1992), lead arsenate (Leclerq and Valliant, 1992), co-proxamol and amitriptyline (Wilson et al., 1993) have been found to be present in maggot tissues.

Place of Death : The deceased may have been killed at a place other than where the body is found. With knowledge about the carrion fauna of an area and specific habits of species found on the cadaver, an entomologist can help to determine whether the person died at a place other than where the body has been found. Similarly, route of transport of a dead body may also be traced by using entomological data.

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