Kevin Neal, Convicted of Murder by Forensic Entomology
The number of different fly species on the planet has never been calculated, but fortunately for forensic entomologists, the species that prefer carrion for food and oviposition are relatively few and often localized to a specific region of the country. In fact, it is not uncommon for scientists to be able to point out that a body has been moved from where it was killed because of the difference between "urban" and "rural" species. And just like different human cultures prefer different foods, necrophilous fly species vary in their preference for decaying flesh. Depending on what species are present (or not) and their stage of development, criminalists can make accurate estimates of the post-mortem interval. They can do this because of the flies' dependence on temperature.
Ideally, entomologists should be part of the initial crime scene investigation so that bug evidence can be collected and preserved correctly. The techniques that work for a collector who wants to pin his or her trophies to a card do not work in a criminal investigation. There are also chain-of-custody issues to be addressed and some methods of storing and preserving insect evidence are counter-intuitive to criminalists who may not have been instructed in how to properly collect bugs.
If the presence of the entomologist is not possible at the crime scene, the next best chance to collect insects for examination is at the autopsy. Finally, a later visit to the scene where the body was found can yield important entomological evidence long after the scene has been cleared. The bottom line for investigators is that if evidence is not collected according to established protocols, the efforts of the best forensic entomologist will be for naught.
"Entomological evidence must be properly recognized, collected, and preserved if such evidence is to be used in evaluations of death cases, writes pathologist Glenn Larkin. "It is only when the physical characteristics of the specimens are intact and properly preserved that an accurate determination to the species level can be accomplished by an entomologist."
At Nettle Creek Cemetery, and later during the autopsy, investigators gathered sufficient entomological evidence to allow Dr. Neal Haskell and Dr. Robert Hall — the former working for the state and the latter for Kevin Neal — to draw vastly different conclusions about the post-mortem interval (the time between Cody and India's murders and the discovery of their bodies). It would be up to the jury, most of whom didn't know the difference between a blow fly and a beetle, to decide which expert among two of the world's top forensic entomologists was correct.