So, what are you doing on Wednesday nights at 9 P.M. EST? While we’re sure that most of you are curled up with your latest forensic science journal in an attempt to stay completely updated on your profession of choice, many individuals in the United States, and even abroad, are channel surfing trying to find something on television to occupy their time. While the interests of many might be sports, cooking shows, or some other form of visual stimuli, we have a particular interest in the television series, MythBusters™ on the Discovery Channel. This show has its hosts, special-effects experts Adam Savage and Jamie Hyneman, tackle three so-called myths each week. The myths investigated are highly varied; however, they often lend themselves to scientific inquiry for validation or debasement.
The beauty of the show is that their results are not always falsification of the myths being investigated. In some cases they actually verify that although seemingly improbable, myths such as detainees being able to make a crossbow from available materials in prison are possible. But, no real worries, the crossbow they constructed might, at its best, poke out your eye.
So, why are we discussing this show? Because it is not only interesting to us as individuals that are entertained through its subject matter on a weekly basis, but that in some ways it struck a chord as it relates to our profession as forensic entomologists. Ideas often initiated through discussion evolve and become “recognized fact.” In the case of forensic entomology, myths about the use of insects as evidence in legal investigations are circulated among the forensic community. These myths, while recognized by entomologists and easily nullified, can be accepted as facts by others. And this type of information can become inhibitory in terms of its application. In the spirit of Myth-Busters,™we review three of the most common misconceptions, or beliefs, about forensic entomology.
1. Myth: Forensic Entomologists can determine the postmortem interval in cases of human death.
Myth busted: Forensic entomologists do not estimate the time of death. Forensic entomologists are not pathologists, and they are not (at the time of this writing) medical doctors. Therefore, any estimation of the actual time of death would be working outside the realm of their expertise.
What forensic entomologists can do is provide an estimation of a portion of the postmortem interval. Specifically, forensic entomologists are experts, and quite good at, determining a minimum estimation of the postmortem interval. We can do this simply because we have an arsenal of data at our fingertips. For decades entomologists have been raising insect species of forensic importance in controlled laboratory conditions. As entomologists, we know the maximum growth rate these insects have under optimal conditions. So, since insects can only grow so fast, even when things are “perfect,” we can take that as our absolute minimum developmental time. We also know that most of the insect species of forensic importance will only feed on dead and/or necrotic tissue. Thus, we know that a particular set of remains must have been deceased before colonization by insects.
Additionally, things in the real world are rarely, if ever, perfect for the development of these insect species. So we now must calculate the various factors that would reduce the insect growth rate below the optimum level. Secondly, we must also consider biological variation. The fact is that some insect larvae will outgrow others of the same species. Just consider a litter of kittens or puppies. Some will outgrow their brothers and sisters. Thirdly, we must consider that a major factor in the regulation of insect growth is the ambient temperature. We may not always know that information with any degree of accuracy. Rarely are human remains from victims of violent crimes found underneath a climate data-recording station. So, we must make extrapolations from data recorded at the nearest station, which may be a number of miles away from the body recovery site. Lastly, we must calculate the delay in the arrival of the adult insects. A history of casework and experimental research allows us to make estimations as to the arrival times of many adult insects.