By: Jeffery K. Tomberlin, PH.D, D-ABFE, John R. Wallace, PH.D., D-ABFE, Jason H. Byrd PH.D., D-ABFE
Issue: October/November 2006
Untitled Document
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 in this article.
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.
Carrion flowers rely on carrion feeding insects as pollinators instead of bees
and wasps as do many other flowering plants. Photo by Dr. J.H. Byrd
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. Photo by Dr. J.H. Byrd
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. Photo by Sue Gruner, University of Florida
Conclusion
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 jktomberlin@ag.tamu.edu.
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 john.wallace@millersville.edu.
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 jhbyrd@ufl.edu.
