University Of Florida Forensic Entomologist Uses Insect Larvae To Track Killers
GAINESVILLE, Fla. — They say all murderers make at least one mistake, and when Jerry Butler is on their trail, it is almost inevitable that he’ll find it.
Butler, a forensic entomologist with the University of Florida’s Institute of Food and Agricultural Sciences, has a sleuthing method that is as gruesome as it is effective: He studies insects that invade human corpses, and by examining growth patterns of larvae, obtains crucial information about the time and place of a human death.
It’s not a subject for the weak of heart — or stomach — but it can be an invaluable tool when tracking murderers.
Butler, one of only five forensic entomologists in Florida and about 100 nationwide, is currently performing an analysis of fly larvae — also known as maggots — for a two-week old murder case in Ocala, Fla. He said if he obtains the right species of fly maggots from the corpse, he can use them to project the “time since death,” or post-mortem interval.
“For entomological evidence to be useful in court, we must know the exact type of maggot we are looking at,” Butler said. “Specifically, we look for one of five key fly maggots that can tell us information about a homicide.”
Butler said two of the most forensically important flies, the Secondary Screwworm fly and the Hairy Maggot Blow fly, can detect and invade a body within 10 minutes of death and thereby give entomologists valuable forensic information.
“If we have one of the key flies, and we know what the environmental temperature has been, we can establish the time of death to within hours, providing the body is found soon enough,” Butler said.
He said the ideal situation is to find the corpse within a week because the error rate goes up exponentially as time progresses. Interestingly, if the body is in a place where it is too cold for flies to breed, that can also be good forensic information.
“The absence of flies tells us a lot too because it gives us a snapshot of how cold it’s been in a given time period. That type of data was useful in pinning down one of the Bundy murders,” Butler said, referring to serial killer Ted Bundy.
In the Bundy case, the absence of maggots indicated the murder took place in Florida during a two-week cold snap, thereby giving police a narrow window of time to focus on.
Of the more than 40 murder cases Butler has worked on, his first job came during a triple-homicide trial in Gainesville in the mid-1970s. He used forensic entomology to establish that all three victims had been killed at the same place and at the same time, thereby refuting the defense attorney’s assertion that the murders were not related.
Because the bodies were found in three different locations — one in a mobile home, one in the bed of a pickup truck and one under a tree — the maggots that occupied the corpses were in various stages of development. The defense said that the different larvae sizes proved the murders took place at different times.
But because maggots are cold-blooded animals, they develop in life cycles that are temperature-dependent. Butler used an “accumulated-degree hour technique” to assess the age of maggots inhabiting the corpses. By using various data including recent weather patterns, indoor temperatures and the size of the larvae, he established that the three murders occurred at the same time, thereby defeating the defense’s assertion that the killings were unrelated.
Data provided by forensic entomologists such as Butler can often help law enforcement agencies pin down a murder suspect.
Ric Ridgway, assistant state attorney for Marion County, Fla., recalled working with Butler in 1993 on a murder case.
“The suspect had an alibi for the block of time during which the victim’s body had been abandoned,” Ridgway said. “UF’s Butler used Blow fly larvae to give us a much narrower window of time. We then used that information to discredit the suspect’s alibi.”
Although forensic entomologists are most frequently used in homicide cases, they also investigate cases involving improper wound care, as in nursing home abuse or child neglect. In addition, they examine animal deaths and food contamination cases.
Butler said his most memorable case involved an illegal shooting of the endangered Florida cougar. In 1990, a hunter shot the cougar, which dragged itself into some nearby bushes. Clinging to life with maggot-infested wounds, the cougar was found via radio transmitter by state wildlife personnel. Fly maggots were removed from the wounds and sent to Butler, who pinned down the shooting time to within a few hours.
When the hunter was confronted with the irrefutable biological evidence, he confessed.
Butler said that although forensic entomology was thrust into the public consciousness in 1990 with the release of “Silence of the Lambs,” it is not a new science.
“The use of insects in forensic work dates back to about 13th century China,” Butler said. “We have built upon that historical base, and it has proved to be quite reliable.”
- Paul Kimpel
- Jerry Butler, email@example.com, (352) 392-1901 x-152