<omes to fauna in the Arboretum, we usually pay most attention to the bigger, brighter, or at least interesting sounding residents. While grazing deer, cacophonous frogs and flittering birds of all varieties are integral parts of our experience of the Arb none of them can help solve crimes.
Speaker Valerie Cervenka came to discuss forensic entomology, the use of insects to aide in legal investigations, with Carleton students and staff last Friday. Though I hadn’t planned to spend my birthday looking at slides of decaying humans and animals, I was quickly drawn into her presentation.
Ms. Cervenka collaborates with homicide investigators, coroners, and medical examiners to put together the story of victims of homicide. Usually her task as part of this team is to find an estimate for the “postmortem interval,” or time since death. After seventy-two hours have passed since time of death, estimates from forensic entomology are the most accurate in assessing the postmortem interval.
Forensic entomologists primarily use the life cycle of flies and their parasites to determine the postmortem interval. Most flies, including the Blow fly (commonly used by forensic entomologists), have a predictable life cycle. The mama fly lays her eggs; they hatch, go through three larval (maggot) phases, pupate, and then emerge as flies. Using the stage of development of the fly and temperature records for the place the body was found a forensic entomologist can draw on previous knowledge of the time it takes for a fly to reach that level of development at that temperature to predict the time since the eggs were laid, usually very close to the time of death.
If you are interested in Ms. Cervenka’s work, or forensic entomology in general, you can find more information at www.forensicentomology.com.
