Fighting Crime With Bugs

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In one case I had to determine whether an individual had consumed cocaine before death. I wondered whether I could use the maggots, beetles, and pupa that had inhabited the body and test them for drugs. The answer turned out to be yes.

Drug use has skyrocketed in the last ten years, as have drug related homicides—so more and more frequently we are looking at the effect of drugs on bugs.

What happens to insects when they take cocaine or heroin?

Cocaine, heroin, ecstasy, angel dust [PCP], and amphetamines all affect a bug's life. For example, cocaine increases the growth rate so the maggots grow more quickly. A maggot feeding on a long-term heroin addict will actually have a slower growth rate compared with a maggot that is found in a new user, or someone who died of an overdose. All these factors are important if you are using the life cycles to calculate the time of death.

What do you use for your experiments? How do you study decomposition?

Generally we use pigs. A 50-pound pig most closely represents human decomposition—it's the next best thing to a human corpse. We have a secure area in part of the university and in various military zones where we can let the animals decompose.

I once put a 50-pound dead pig wrapped in blankets in my backyard to decompose to mimic a body in a homicide case—we were trying to determine how long it takes insects to penetrate the wrapping.

We also put the animals in a range of different environments—in rain forests, arid volcanic craters, tidal pools—to see how conditions change the rate of decomposition. We have hung pigs in trees to see how decay differs from when the animal rests on the ground. We've buried them and burnt them to varying degrees to see the effects.

Rates of decay can vary wildly. In Hawaii's rain forest a body can be stripped to the bone in as little as 18 days. In an arid environment there can still be flesh on the bones after a year.

How do you determine time of death?

We look at the succession of bugs that have infested the body. In Hawaii, within 10 minutes of a death, female blowflies will begin to investigate the body openings—eyes, ears, nose, mouth, anus and genitals—and begin to lay eggs. This essentially starts the biological clock.

A dead body is a bit like a barren volcanic island. As plants begin to take root they make the island much more inviting—same with the body. As the maggots hatch and feed they attract predators and parasites. Then come flies, beetles, and parasitic wasps, all within a few days. By day five you have houseflies, then more beetles and so on—an endless parade of insects.

Even at the skeletal stage there is still a lot going on. The fluids that have seeped out of the body have changed the character of the soil—that's when the study shifts to the soil. There you look at the fungus and algae. Even one and a half years after death there will be detectable stains and a telltale selection of arthropods.

Depending on which bugs are there, and when, and the stage of development, you can estimate the period of death.

How many species of bugs will infest a corpse?

In Hawaii, more than 300 species will visit the body from the time of death through the skeletal stage. On the mainland more than 600 insects can pass through a body. Some people are just a lot more popular dead than alive.

What else can you learn about the deceased person?

You can tell if a person was moved after death. If you find evidence of city bugs in a person found in the country you know the body was moved.

You can also determine cause of death. If the insects depart from the normal routes of colonization, like entering through the chest, you might be able to point out an injury that would have been missed.

I had one case where the blood inside a parasitic insect—actually a crab louse—matched the blood of a rape suspect.

We have also used maggots to detect abuse. Looking at how badly a sore was infested revealed how long an elderly person was ignored in a nursing home.

How did you become a consultant for a TV show?

The writers read my book A Fly for the Prosecution: How Insect Evidence Helps Solve Crimes and picked out cases for shows in the first and second season. Now I generally talk with the writers on a biweekly basis. The main character is a forensic entomologist. If you had told me 20 years ago that there would be a crime show with a forensic entomologist as the main character I think I would still be laughing.

You are also curator for the traveling museum exhibit CSI: Crime Scene Insects?

Yes, I was asked to curate to make sure the exhibit is scientifically accurate and palatable. It's a lot of fun. Forensics is a great way to trap kids into appreciating science.

On TV: Biography of a Corpse airs Monday, April 26, at 9 p.m. ET/PT in the United States and is available only on the National Geographic Channel.

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