- Crime Lab
- Crime Scene
- Death Penalty
- Digital Forensic Insider
- Digital Forensics
- Evidence Collection
- Expert Forensic Voices
- Forensic Anthropology
- Forensic Psychology
- Impression Evidence
- Medical Examiner
- Mobile Forensics
- Police Procedure
- Sexual Assault Investigations
- Witness Testimony
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.
As you can see, there are many variables that will lengthen the insect growth rate from its optimum condition. Of course, this leads to a degree of variability for the more “maximal” postmortem interval estimation, and longer postmortem intervals lead to more variability. However, if you want to know the absolute minimum time a particular set of remains has been deceased, a forensic entomologist is a good person to know.
2. Myth: Entomological evidence recovered from decomposing human remains can be used to detect and quantify the level of narcotics present.
Myth busted: Over the course of the past twenty years toxicologists working in conjunction with forensic entomologists have been investigating the analysis of entomological evidence recovered from decomposing remains for the presence of drugs.
Initial evidence from these studies was very promising. Data indicated that insects could serve as a resource for detecting these substances when other typical sources, such as urine, blood, or tissue, were not present. At some point the myth that insect evidence could be used as a resource for detecting target compounds evolved into the concept that these insects could be analyzed for quantifying the concentration of compounds within a corpse. While some evidence supports the hypothesis that insects can be used for detecting these substances, data indicate that with certain compounds e.g., narcotics, insects sampled from human remains may not be a suitable substrate for quantifying these compounds. However, it is important that both entomologists and toxicologists recognize the limitations but also the possibilities of quantifying other inorganic compounds such as pesticides as they relate to a time of application.
The Hairy Maggot Blow Fly (Chrysomya rufifacies) is an introduced species in North America. It is the only North American blow fly that is both cannibalistic and predatory. Here, it is serving as a pollinator for a Carrion Flower, Stapelia gigantea.
Today, forensic entomologists recognize two important aspects of entomology as it relates to toxicology. One, as previously stated, insect evidence collected from human remains can be used to detect the presence of drugs. And, in some cases when the primary resources used for toxicological analysis are not present, insects collected from the corpse may serve as an alternative material for examination. Two, it is important to know if narcotics were ingested by the decedent if entomological evidence is being analyzed for determining the minimum postmortem interval. As stated in the first myth reviewed, many variables can influence the development of insects developing on a human corpse. The effects of select narcotics on the development of forensically important arthropods have been examined. Information determined on these compounds indicates that their effects might be to increase or slow down the growth rate of certain fly larvae depending on their stage of development. However, many synthetic materials that have been developed in recent years have not been investigated.
"Southern Pearly-eye" (Enodia port-landia), which is locally abundant throughout the Southeastern U.S. Butterflies such as this may be commonly found at scenes involving human death where they feed on sugar rich body fluids. The forensic investigator should take note of butterflies, bees, and wasps as their presence may be valuable information to the forensic entomologist.
3. Myth: Forensic entomology only revolves around death-scene investigations.
Myth busted: Midway through this article you reached for the peanut butter jar and returned with a sandwich only to realize that the brand you purchased was smooth and the crunch was a beetle encased in the buttery matrix. Often forensic entomologists are called upon to testify in court on entomological issues unrelated to death-scene investigations. After all, the topic of forensic entomology by definition implies the use of any insect evidence in the court of law. Besides medico-legal or death-scene investigations, other examples of how entomologists have contributed expert testimony include: stored or commercial products and urban or structural issues involving buildings such as homes, apartments, and industries.
The process of producing stored or commercial products, such as food and beverages, much of the time begins in the field or involves automated processing procedures during which insects and other organisms often find their lives integrated with the final product. Consider that the Federal Drug Administration (FDA), as well as the United States Department of Agriculture (USDA) regulates the amount of insect particulate matter allowed in your favorite food item. Insect matter in food is not allowed if the amount present surpasses the Defect Action Level (DAL) published for that food item. So, you can relax in knowing that the average individual in the United States consumes about one pound of insects per year as part of their normal diet. Some forensic entomologists serve as consultants for major commercial food/beverage companies and are asked to provide expertise in cases regarding the contamination of these products with insects and other arthropod parts. For example, entomologists have testified in cases involving candy bar and beer infestations of arthropods. In these instances, the forensic entomologist must determine if contamination occurred while the product was still in the plant or after purchase by the customer. Barcodes on commercial products provide very useful information in such cases, e.g., date product left plant, shipping date to store/restaurant, and shipping trucks that help narrow the time frame of when insect contamination may have occurred.
Annually, real estate sales and purchases are a multi-billion dollar industry. Building codes and subsequent inspections for insect-related damage on infestation is federally mandated. Consequently, homeowners must provide formal documentation that their home is free of insect damage or infestation such as from termites or cockroaches or possibly face legal action against them. Other insects besides cockroaches and termites are a concern for the urban environment. Due to increased worldwide travel among people from all nationalities, most recently, there has been a resurgence of bed bug infestations in hotels and other public lodging structures. While bed bugs feed on human and other animals for a blood source to produce eggs, they do not transmit any disease. However, make no mistake, a client waking up in the morning discovering blood drips on an arm or leg from the previous night’s feeding activity by the resident bed bug population, is enough to cause trauma and resultant legal actions against said hotel ownership. A forensic entomologist may be called to trial to testify on any insect evidence related to urban settings or structural issues.
|The Flesh Fly (Sarcophaga haemorrhoidalis) has a preference for indoor environments. It also has the ability to give live birth. The fly's quick movements and ability to deposit a live larvae helped give rise to the early theory on the "spontaneous generation of life."
Photo by Dr. J.H. Byrd
Adult black soldier fly, Hermetia illucens L., depositing eggs.
It is our hope that this article illustrates that forensic entomology is not “junk science,” or even voodoo. It is a science that deals with biological organisms and biological variation. Forensic entomologists can quantify this variability, and are working on methods to enhance the statistical certainty of the science. That said, forensic entomology can certainly be misapplied. It is likely that nearly every forensic science professional can cite a case in which some aspect of forensic science has been misapplied to the detriment of the science. Certainly forensic entomology is not immune. It is relatively rare that forensic entomology is relied upon solely to assist in determining the possible postmortem interval. Most commonly it is used as supporting evidence for other items of physical evidence, or the statements of suspects and eyewitnesses. Perhaps the true utility of forensic entomology is its role as supporting evidence. One fact that holds true for almost every case involving forensic entomology is that if it is utilized (when present), it will yield information relating to the crime that is impossible to obtain otherwise. We now return you to your regularly scheduled program.
Jeffery K. Tomberlin, Ph.D., D-ABFE is Assistant Professor and Extension Specialist at Texas A&M University Texas Cooperative Extension. Jeff can be reached at firstname.lastname@example.org.
John R. Wallace, Ph.D., D-ABFE is an Associate Professor in the Department of Biology at Millersville University, Millersville, PA. John can be reached at email@example.com.
Jason H. Byrd, Ph.D., D-ABFE is a Forensic Entomologist at the University of Florida, Department of Criminology, Law and Society. Dr. Byrd can be reached at firstname.lastname@example.org.