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Murder mysteries captivate
this Sherlock Holmes
of insects"A Fly For the Prosecution: How
Insect Evidence Helps Solve Crimes"
By M. Lee Goff (Harvard University Press, ISBN 0-674-00220-2, $22.95).By Burl Burlingame
Star-BulletinOF ALL THE MYSTERIES surrounding death -- biological, philosophical, epistemological, spiritual -- here's one that's purely entomological: How do flies know when you die?
"No one knows," marvels M. Lee Goff, entomology professor at the University of Hawaii at Manoa.
"Flies will travel great distances within minutes of death. How do they sense it? It's a mystery. Some species of blowfly even seem to anticipate death, and will gather and wait."
The flies aren't spectators to death; they're enablers. Within minutes, flies will gather at the oozing openings on a corpse -- mouth, eyes, wounds -- to feast on the liquids and to lay microscopic eggs. Within a day, the eggs hatch and maggots begin to consume the corpse. These in turn attract other insects.
With allowances for variables such as coverings, temperature and humidity, this is a predictable, tiered outcome, and experts -- such as Goff -- can deduce from a carrion insect's age how long a body has been dead.
In cases of murder, this is a good thing to know. Goff is one of a handful of "forensic entomologists" in the world, a Sherlock Holmes of insects, and is likely to become better known soon, thanks to his engaging study of a horrific process, "A Fly for the Prosecution: How Insect Evidence Helps Solve Crimes."
Working as a pathologist in the Army, Goff learned not to be spooked by the dead, and later, as an entomologist at Bishop Museum, he became a specialist in acarology, the study of mites and ticks.
In the early '80s, at a convention for the Entomological Society of America, Goff was staying across an eight-lane freeway from the event. "The museum's $18-a-day per diem couldn't cover hotel rooms at the actual hotel where the conference was," he said. So he hiked in early, and trudged out late, and as a result, wound up seeing lectures he would have normally skipped.
One talk, by pioneer forensic entomologist Lamar Meek, examined the life cycles of insects as played out against the mystery of murder. As ghastly slide after ghastly slide played on the screen, and half the audience stampeded for the door, Goff was transfixed.
On his return to Honolulu, Goff began pestering then-medical examiner Charles Odom for a chance to work on a local murder case. It took awhile, partly because Hawaii's unsolved murder rate is low and partly because Odom's secretary thought he was nuts. Eventually, Goff "looked at a couple of cases and got close on the dates, and they started pulling me in on a regular basis."
The educated guess
Goff estimates that 98 percent of his goal in forensic entomology is figuring out the time that has elapsed since a person's death. Insects multiply on a strict timetable, that part is fairly cut and dried. But variables such as temperature, humidity and whether the insects can get to the corpse come into play, and that's where educated guesstimation comes in.Raw data is collected from the corpses of 50-pound pigs, which replicate best the head and trunk of the average human. The animals are placed around Oahu in various climates and monitored.
For example, in a late '80s case involving a dead woman tightly wrapped in rugs and dumped in the open, Goff estimated the insects on the corpse were 10 days old. "But that's 10 days from the time the insects actually reached her, and they were impeded by the wrapping. So I wrapped a pig exactly the same way and dumped it in my back yard -- my dog thought it was great! -- and observed it to see how long the insects took. They are surprisingly determined when they know food is in there."
It took the insects 2-1/2 days, leading to a time-of-death estimate of 12-1/2 days -- exactly matching a missing period in her estranged husband's alibi. He was convicted.
Under straightforward conditions, the estimated time of death can be very precise. In a California case, Goff studied the data and estimated that death had occurred between 10 p.m. and midnight on April 14, a couple weeks before. When he called the homicide division with this estimation, the line went silent, and Goff thought they were laughing at him.
They were actually shocked. A suspect had just confessed to committing the murder at 10:30 p.m. April 14.Such accuracy is thanks to data collected from the test animals, and a thorough understanding of how insects contribute to the process of decomposition.
"A corpse is like an island in the sea, different from the surrounding environment," explained Goff. "It is an instant source of nutrients, an expendable resource, and what happens to it affects the site it's located in as well."
First to arrive are the flies, who go for the easy meal of body fluids. Their larvae, which hatch 12 to 18 hours later, are called maggots, and the maggots have three size cycles called instars before they leave the corpse, create a cuticle shell called pupae and begin to metamorphose into flies.
Maggots feed on rotting flesh by using tiny mouth hooks and spewing digestive enzymes before them, turning the shredded flesh into a kind of soup. (Maggots are useful on the living as well, cleaning bed sores and gangrenous wounds with surgical precision.)
Decomposition produces bodily fluids with a high ammonia content. It leaks from the corpse, attracting other insects and also soaking the soil with alkalinity. "You can usually tell where a body has been in the wild," said Goff. "The site looks different; different plants, different insects, different smell and feel. The traces remain for years."
The maggots become targets for insects such as wasps, ants and beetles. As the corpse dries out, other insects move in, such as hide beetles that like nothing better than mummified skin.
The process isn't pleasant, but it's highly efficient. In Hawaii, a body can become a skeleton within a couple of weeks. Even after the insects are finished, they can leave behind evidence such as tiny pupae cuticles that contain trace amounts of any drugs the victim was using.
Aggressors before death, too
Even though blowflies can sense death, they also can become determined aggressors after the living, in certain circumstances. For example, the infant abandoned on the shores of Lake Wilson a few years ago became exhausted and stopped moving, and the fecal matter in the baby's diapers attracted flies. When she was found, maggots swarmed in her diaper, and a time of abandonment could be determined."That case got bumped up to the state Supreme Court because the defense team believed the fact that the baby was already being attacked by maggots before death didn't look real good for their client," said Goff.
Bodies don't decompose on a laboratory schedule. It's also a mystery why dogs seem to love the scent of rotting corpses. "FBI people have told me a surprising number of missing bodies are found when Rover drops something on the front step that he shouldn't have," said Goff, who helps train FBI agents in insect-evidence collection.
If a pet is locked in with a deceased owner with no access to food, cats will invariably eat the face first, dogs the genitals and entrails. But if a dog finds a skeleton, they seem to believe the skull is a chew toy. "We often find little triangular holes from dog teeth" in the superorbital ridges and nasal shield of a skull, said Goff.
As for Goff himself, does he plan to become worm food?
"Not me! Cremate me and dump the ashes out at Kaisers, my favorite surf spot," laughed Goff. "To heck with the bugs."
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