Differences in Post-Mortem Interval Estimation Determined from Dismembered Remains Versus Intact Bodies Using Forensic Entomology

ABSTRACT
Insect succession studies on human remains has increased following the University of Tennessee’s early 1980’s work. (Rodriguez & Bass, 1983, 1985). Several factors complicate using Forensic Entomology to determine Postmortem Interval (PMI). Insects demonstrate a wide temporal range and spatial diversity, making it difficult to predict which species will be present. Additionally, consistent patterns in carcass size preference with carrion insects has been observed. (Kuusela & Hanski, 1982) This study compares data collected from 5 dismembered porcine remains in Central Virginia to data collected from the University of Tennessee and other sources used determining PMI in whole corpses.

In a far corner of George Mason University’s Science and Technology campus is a plot of land set aside to allow students to study taphonomy – the decomposition of remains.

With the help of my mentors, Dr. Rebecca Forkner and Dr. Anthony Falsetti, I am using this “Remains Laboratory” to study the succession of insects that consume a body as it decomposes.

My goal is to apply this information on species abundance and time of arrival to the estimation of time of death.

Many previous studies have determined the order of insect succession on full body remains, but few have examined insect succession on remains set out into the environment in pieces.

Law enforcement has identified this as an unfortunate but needed area of study because recent gang-related activity has involved dismemberment.

When remains are found out in the elements, a timeline of events is an important part of the investigation.

The ability to determine time of death can be difficult if the remains have been outside long enough for them to have gone through a significant amount of decomposition.

Sometimes, the only way to determine a Postmortem Interval or PMI, is by examining the insects present, their ages, and the number of generations they have produced.

Forensic Entomology is the area of forensic science that uses these insects and when they arrive at remains to determine PMI.

I’ve begun my research using pig remains, as a close comparison to the composition and structure of humans. However, I intend to continue the study with human remains as soon as the Forensics Department can fund cadaver use and accept donations.

My investigation is composed of five pairs of remains. Each pair consists of several pieces of pig limbs, and one set is placed on the soil surface, and the second set is buried approximately 30 cm deep. Each set is then covered with a protective wooden box. The boxes are open to the elements with two layers of chicken wire to protect the remains from scavengers.

I set up two mechanisms, other than hand collection, to capture and record the insects visiting each pair of remains. Pan traps and fly traps collect the insects that come into contact with the remains.

My volunteers and I then collect insects on a daily basis and identified them in the lab to record succession and quantify insect diversity. In the lab we sort and identifying the insects collected into families and orders by date and individual remains.

This will provide a timeline of which insects arrived at what time and in what numbers.

We will then compare the data we have collected to data that has been compiled from past published students.

I am looking for the clear distinction of a different type of succession from what will arrive at fully intact remains. Generally, insects that are attracted to full bodies include blow flies and flesh flies that attack open orifices like the eyes, mouth, nose, and ears.

My prediction was that some insects will arrive sooner than on full bodied remains because tissue is already exposed and that some may be present for a shorter period of time because less tissue is present at the start.

So far, I am seeing an increase in the beetle population, as well as a different arrival time of those beetles. In my study, they have arrived earlier than anticipated.

The blow flies, house flies and flesh flies arrived first on to lay eggs on the remains.

The succession of those insects has followed a consistent pattern and been predictable based on prior studies.

However, the remains decomposed at a faster rate because they have open wounds.

This caused the duration of time that the main carrion fly species were present to be much shorter.

The remains are now in the active decay stage.

The larvae of the flies who have visited and laid eggs are now prevalent, as are beetles. We are still in the process of compiling the data collected, but so far it has been a successful and interesting in results compared to previous studies.

Much of this information is important because it will show the types of carrion insects prevalent in the area of Northern Virginia at this particular time of the year.

It will be useful data to compare to when we are able to use human remains in the near future.

It will be information that can aide in death investigations in Northern Virginia to determine how long remains have been out in the elements and will be helpful in determining time of death.

I would like to thank the Office of Student Scholarship and Creative Activities at GMU, without whose for the guidance and funding, this project would not have been possible.