By: Madlen Wendland
When investigators arrive at a
crime scene and insects are crawling all over the body, it might be unsettling
for most people, but for forensic scientists, those insects provide some of the
most valuable evidence in an investigation.
Forensic entomology is the
scientific study of insects in legal investigations, allowing scientists to
estimate how long a person has been dead. By examining insects’ activity on
decomposing remains, experts in biology, ecology, and environmental science can
determine a more accurate time of death.
“Entomology is the study of
insects, and forensic entomology is the study of insects associated with a dead
body, which can be a human or an animal,” Gail Anderson, professor at Simon
Fraser University and co-director of the Center of Forensic Research in Canada,
said.
The first insects to reach the dead
body are flies, especially the blowfly species. Flies have to find something
that is decomposing and dead in order to lay their eggs, and for those eggs to
develop.
Edward Mondor, associate professor
of biology at Georgia Southern and interim director of the Center of Forensic
Science in Georgia, said that insects are so important because they cannot
regulate their body temperature on their own. Therefore, their activity and
development are strictly dependent on environmental temperature.
“Insects are just simply little
bags of chemical reactions, and like everything you learn in chemistry, the
warmer it is, faster reactions go, and the colder it is, slower reactions go,”
Mondor said. “Because insects cannot regulate their body temperature, we use
insects just like a biological clock that will help us determine how long the
person has been deceased.”
The flies are laying eggs on the
dead body, and those eggs will later hatch into maggots, which will further
develop into adult flies. In order for flies to complete their life cycle, they
have to find something decomposing.
“We as forensic entomologists use
this to our advantage and basically just look at the development stage of the
insect, which can tell us an estimate of how long the fly has been on the body,
which ultimately helps us to determine how long the person has been dead,”
Mondor said.
Laurie Baio, assistant district
attorney and prosecutor for the Atlantic Judicial Circuit, mentioned a recent
murder case of a female Georgia Southern alumnus in 2023, where forensic
entomologists were able to identify a correct timeline of her death and uncover
various lies that the murderer spun.
“We found her body in six different
parts, and when the investigators discovered her right leg, they scooped up
some of the maggots and placed them in a container for further examination,”
Baio said.
After analyzing the fly and
identifying its species, the entomologists used the time and temperature
recorded during recovery to determine the life stage of the maggots and when
they began feeding on the victim's remains.
“By determining that we created a minimal
postmortem interval,” Baio said. “Which means that the investigator knew the
first time when the bugs could have been introduced to the carcass, to the time
when we found the remains.”
With knowing the estimated period
of her death, they were able to uncover lies about her time of death, which her
husband had previously told law enforcement, and they ultimately convicted her
husband of her murder.
Using this method differs from
traditional forensic techniques. This is because after the person has been dead
for more than 72 hours, the traditional methods do not work anymore.
“There are multiple problems with
traditional techniques when a body is found after 72 hours,” Anderson said.
“Algor mortis, livor mortis and rigor mortis cannot be applied anymore after
some time has passed, after the body has reached certain conditions.”
Algor mortis is the cooling of the
body temperature after death; livor mortis is the staining of body tissues that
causes discoloration of the skin; and rigor mortis is the stiffening of the
muscles. However, all the processes are no longer reliable after 72 hours of
death.
That is why experts use the insects
that are found on the body if remains are found after this initial time period.
Jeffrey Tomberlin, professor at
Texas A&M University and the director of the National Science Foundation
Center for Biomanufacturing and Innovation, said that forensic entomology can
be applied to recent cases as well as to much older ones.
“You can have bodies that are dead
for millennia, and by knowing the insects associated with it, you can say it
was a certain time of the year,” Tomberlin said. “An example for that is the
Innocence Project”.
This project is known for taking on
cold cases involving people who have been previously convicted, reopening them,
and working with entomologists to prove their innocence.
Mondor said that new technology and
its development have had a significant impact on forensic science and will
continue to do so.
“Probably 20 years ago, there was
no way that we could analyze insect behavior and their genetics,” Mondor said.
“If we now have a case and for some reason cannot look at the insects under the
microscope due to their conditions, there are different paths that we can
follow in order to get our information.”