Forensic Entymology: How far does it take us?

Entymology—The study of insects. This practice has been used for years by forensic scientists to help solve the mysteries of crime scenes. This method was popularized even further when Gil Grissom, the CSI Las Vegas television series, emphasized the use of bugs found at the scene to help reveal mysteries about the body.

I found an interesting article, "The tell-tale grasshopper: Can forensic science rely on the evidence of bugs?"(mentioned in both news@nature.com and WIRED magazine) in which the identities of four bugs (along with other evidence) were used to convict a man with murder.

In this article, Vincent Brothers was tried for killing his wife, mother-in-law and children in Bakersfield, California. The main evidence used against him were the four bugs that Lynn Kimsey, an entomologist at the University of California, Davis, revealed during the trial. "A grasshopper, a paper wasp and two 'true bugs'...[showed] that Brothers' rental car had been well beyond St Louis" (Ledford's article). The scientists argued that these insects were indigenous to areas found only west of Missouri, thus indicating the car had traveled west of St. Louis.

Even though the accused said that he drove the car no further west than St. Louis, Missouri, the enymologic evidence said otherwise. Although, one has to question: how accurate can this type of investigation really be? When working with dead bodies, it is reasonable to scrutinize the developmental stages of maggots found around the body to estimate how long the body has been dead. However, when looking at insect carcasses that are plastered on a rental car's radiator and air filters, there is so much uncertainty about how and when the bug got there along with the transportation mehtod, that it is hard to imagine such evidence would actually be looked at seriously in court.

It is true that investigators have been using "insect informants for centuries, typically focusing on the flies that colonize dead bodies, [and] if the conditions are right, such bugs can reveal how long a body has been dead, if the victim was poisoned, or wheter the body has been moved. Bugs can also help to track movement -- a squashed bug plucked from somen's shoe treds or a revealing insect bite form a geographically limited pest can all be clues of where a suspect has been" (Ledford's article). But this type of detective science is based on the geographic location of where bugs are normally found, and there are no distinct lines that can be drawn, as they did in this trial with the boundaries of various insect's habitats.

Sure, an approximate area could be estimated, but the fact that an exact line was drawn to divide where one species of grasshopper or wasp was found seems flawed. With migration and climate changes, along with the reliance on outdated maps of these insect’s natural distribution, such claims can not be rightfully presented in the courts.

Forensic science is the application based on the analysis of evidence to answer questions of interest for the legal system; however, as the article also states, the clues scientists use can be uncertain. Thus, even Kimsey, one of the 137 witnesses that took the stand in this case, worries about the skills entomologists employ to determine the identity of bugs.

With modern technologies at investigator’s disposals, having claims of any uncertainty or dependence on an outdated map is unacceptable to have as evidence presented in the courts. As Jeffrey Wells, a forensic entomologist at West Virginia University in Morgantown, declared, “"We have classic publications about bug distribution from maybe 50 years ago that are quite good, but some things have changed. Some distributional records are out of date." Thus, with the idea that insects may wander outside their areas through either natural or unnatural (by hitching a ride on a truck, etc) means, a jury couldn’t possibly consider this when decided on a murder case.

Such evidence, I think, should stick to describing dead bodies; otherwise, the system will convict the wrong man for murder because the fact of bug migration and climate change are being overlooked.

This article brings out an uncertainty that scientists need to address. As one blogger noted, “Maybe I just haven't seen the right episodes, but wouldn't it be nice if CSI did a show on just how unclear forensic technologies can sometimes be?” This is a valid point, as the reliance on technology to identify the species increases, the reliance on natural intuition and classical morphology disappears, and investigators look at the bugs only through a machine, rather than through their own eyes.

Although, with the reliance on genetic sequencing, scientists are using only a small database, as all the genes of various insects have not yet been sequenced nor do I think they will ALL ever be. So that means it's back to the basics--learning the morphology of insects the traditional way, rather than waiting on a machine or an archaic map to decide the correct identity and location of an insect.