Forensic Entomology: How Bugs Reveal the Time of Death
(It's a long read, to be sure. But this is something that I wrote for school a couple weeks ago, and I thought that you might like it. :D )
What is Forensic Entomology? To simply put it, it’s the study of biology of insects used to obtain legal evidence in investigations. Entomologists go to the crime scene, and study the development of bugs on the dead body so to estimate the time of death. Scientists, by studying the hatching of the eggs and the cycle of development of larvae to pupa and then to the adult fly can be documented well enough to correctly estimate when death has occurred.
Nature can be kind to Entomologists, because the duration and development are very regular for insects. First off, different bugs arrive at the body at predictable times. And since every insect undergoes predictable stages from birth to death, pending on the current stage scientists can estimate how long the victim has been dead. (Goff 42)
Attracted by the smell of blood from at least 1 mile¹, Adult female blowflies will arrive minutes after death and lay their some 200 and 500 eggs. 23 hours later of moderately warm weather, the eggs will hatch into larvae, also known as maggots. This beginning stage they are called first instar maggots. After two days of developing in moderate outdoor weather, the larvae grow turning into second instar maggots. The larvae then turns into instar maggots by the third day and can move around a bit. When the 8th day arrives, the maggots are now in the pupa stage and wrap themselves in cocoons. Once 14 days come to pass, the now Adult blowflies come out of the cocoon and find another corpse to call home. Then they lay their eggs, and the whole process is repeated. (Denega 48-49)
Bugs like to eat everything. The insects like to feed on the body tissue and dried flesh. The nose, eyes, and mouth of the body is a favorite food source that the Adult blowflies like to lay their eggs on. And then some bugs like to eat the other insects that are already on the corpse. Insects also like to eat the fly eggs and larvae. Some of them also like to feed on the fluids draining out of the collapsing body. Once all flesh has been eaten, the bugs will then begin eating the body’s dried skin and hair.
Insects are partial to anything moist and protected on a deceased person’s body. Bugs will gather on the eyes, ears, and nose. If the mouth was open, they can be found there too. Insects will also locate themselves on open wounds, wounds that may have been there before death, wounds that may have caused death, or wounds that inflicted upon the now-dead corpse. Insects will also be found around the genital areas.
According to “Insect Evidence” by Michael Martin, there are over 90 kinds of blow flies in the United States. Flesh flies typically lay their eggs four days after the person dies—when the corpse is bloated. Beetles are attracted to the dry flesh and will eat it after 24-36 hours. After 48 hours of decay however, spiders, millipedes, and mites will arrive and eat the very bugs that had been feasting upon the corpse.
Each species of Insect live a very organized life. There is almost no variation in their cycle, and because of that, scientists can determine how long a person has been dead. If the body is found covered with flies—not eggs— but have no odors or other signs of decay, then the body has been dead for less then 1 hour. Once eggs have been laid, and are now hatching, the person has been dead for at least 12 hours. As the body begins to dry out by 24-36 hours, the beetles will come and feast upon the dehydrated fleshy tissue. By the second day, spiders, millipedes and mites come and will eat the insects that were already on the corpse. So, because each species of bug will come at specific stages, Entomologists can safely estimate when someone has died.
The location of death can sometimes be established by insects. But this is based on where you know a particular bug lives. “For example, a body was found off of I-75 in Lake City, Florida, dumped there. When the insect specimens were collected from the body, it was realized from the specimens that the species didn’t occur in Florida. They weren’t found south of Tennessee. They found out that the person had been murdered in Detroit, driven two thousand miles, and dumped in Florida.” (Fletcher 195)
Figuring out the time of death is one of the most important things that anyone could to at a crime scene. Such information is vital in telling you who was the last person that was with the victim. It can also indicate where the person might have been last. Plus, if you can find out who was last with the victim just before he died, it may clarify who killed him.²
There was another case where the prosecution declared that an ex-vice principal drove a rental car from Ohio to California with the intent of killing five of his family members. But the defense argued that the car was never in California, and never left the Ohio borderline.
One of the 137 witnesses—who happened to have a good understanding on Entomology—told the court “several insect species picked from the car parts are found only in the West and one was abundant in California. They included that because a large grasshopper, a paper wasp, and two ‘true bugs.’ (A true bug is a wingless or four-winged insect in the order of Hemiptera, with mouthparts adapted for piercing and sucking.).”
Now the interesting thing was that the two true insects could only be found in the West, and both of these can be found in Utah, Southern California, and Arizona. The grasshopper can be found in the eastern slope of the Rockies and in the Great Plains. The particular wasp found in the car is abundant in California. ³
Another thing of interest to this case is that when the scientists picked off from the car insect parts, they noticed that they found no butterflies whatsoever—no sulphur butterflies or painted ladies. With that evidence, it was revealed that the car was driven during the night, not the day. Plus the insects found “were consistent with two major routes to get to California from the East, ‘adding that court testimony revealed “4,500 unaccounted-for miles” on the rental car”’.” This information was used to prosecute the suspect. (Davis)
Another case: On June 23 of 1989, two scuba divers found a woman’s body was inside of a car at the bottom of the Muskegon River in Michigan. As investigation began, police began to wonder when this woman had died. So, they brought the body to a medical examiner for an autopsy to figure out what how she, Hye-Yon Smith died. The report came back as she did not die from an accident, but was murdered by blows to the head. Questions as to when she died arose. Her husband, David Smith, told the police that he and his wife argued on the night of September 30, 1988; he told his friends that he “heard” from her in January 1989. So, with that statement there, the husband became the main suspect.
To test the husband’s declaration, police brought in a forensic entomologist, Dr. Richard Merritt in July 1989 to perform some tests on insect specimens from David Smith’s car. By doing this, Merritt could use the insects to figure out when the car sunk into the river. By identifying several types of bugs, one he found proved to be very useful: black fly pupal casings. In Michigan, black flies will lay their eggs in the late spring or early summer. The eggs then get buried in the dirt at the bottom of the river. For a while, nothing changes. Neither movement nor growth happens. But when fall and early winter comes around, the pupal will hatch into larvae. So, after the larvae goes through their different stages of growth, they become adult black flies in May of the next year. They spend one to two months mating and laying eggs, and then they die.
But what Dr. Merritt learned was that when the car was found, it held empty cocoons. Which means only one thing: the larvae inside had become flies and then flown away. And then that means that they must have been attached to the car by winter of 1988 before Hye-Yon was murdered. Now remember that David Smith claimed that his wife was still alive in January of 1989. According to the tell-tale flies, David Smith had been lying. David Smith was convicted of murdering his wife, and then pushing his car with his wife’s body in it into the river to make her death look like an accident. Ad Dr. Merritt said, “The man was convicted of murder, based in part on the life cycle of an insect.” (The Woman in the Sunken Car)
Every Forensic entomologist needs equipment and supplies in order to do their work properly. Here is just a few of what is needed. Aerial insect nets are essential to the forensic entomology collection in that, to catch bugs from a certain area will certainly help a scientist. Vials are also important because they can be used to hold samples for a short period of time. To have proper Forceps is a must; they are quite useful in collecting specimens without harming them. A collection container for the Entomologist is important in the processing of crime scene because larvae must be collected and sent to the forensic entomology “for rearing purposes.” 4 But most importantly, a 35mm Single Lens Reflex camera, lens, and flash for on scene macrophotography of insects are all needed. Also used are standard 35mm lens, whose sole purpose is for taking general scene photographs.
Bugs are the Forensic Entomologist’s best friend. Because insects like to feed on dead bodies, and live very organized lives, police can determine when some victim has died. Because certain insects only live in certain areas, police can determine where the victim as murdered. Could this be a technique that will become dominant over other techniques of Forensic Science? It will be interesting as the years go by to see what happens with this rather new science. Because scientists can study full cycle of the development of larvae and then to the adult they can correctly estimate when death has occurred.
¹Insect Evidence Page 11
²Every Contact Leaves a Trace Page 195
Fletcher, Connie. Every Contact Leaves a Trace. New York: St. Martin’s Press, 2006.
Gibson, Dirk C. Clues from the Killers. London: Praeger Publishers, 2004.
Goff, Lee M. A Fly for the Prosecution: How Insect evidence Helps Solve Crimes. Cambridge: Harvard University, 2000.
Denega, Danielle. Gut-Eating Bugs. New York: Scholastic Inc., 2007.
Hallcox, Jarrett and Amy Welch. Bodies We’ve Buried. New York: The Berkley Publishing Group, 2006.
Lee, Dr. Henry C. and Jerry Labriola, MD. Dr. Henry Lee’s Forensic Files. New York: Prometheus Books, 2006.
Ferllini, Roxana. Silent Witness. Ontario: A Firefly Book, 2002.
Martin, Michael. Insect Evidence. Minnesota: Capstone Press, 2007.
Tilstone, William J., Kathleen A. Savage, and Leigh A. Clark. Forensic Science: An Encyclopedia of History, Methods, and Techniques. California: ABC-CLIO, 2006.
Walker, Maryalice. Entomology and Palynology: Evidence from the Natural World. Pennsylvania: Harding House Publishing Service Inc. 2006
Chang, Maria L. Science World. Fly Witness. [Updated 1 Oct. 1997.]
Byrd, Dr. H. J. Forensic Entomology. [Copyright 1997-2007]