At crime scenes such as the home of suspected serial killer Anthony Sowell, bug expert Joe Keiper uses insects as clues

sowell-crowd.jpgA crowd watches as investigators search the Imperial Avenue house of Anthony Sowell on Oct. 30.

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CLEVELAND, Ohio -- On the day before Halloween, as grim-faced detectives and crime scene investigators searched the foreboding house where suspected serial killer

lived, a man arrived carrying a folded butterfly net and a small blue fishing tackle box filled with glass vials and surgical tweezers.

Joe Keiper spends most of his days in a basement lab at the Cleveland Museum of Natural History, a bright space that holds cabinets stuffed with hundreds of thousands of carefully preserved insects. It's a bug-lover's dream.

This afternoon, Keiper descended into a nightmare. In the dank basement, police had unearthed a decomposed body from the dirt floor. It was the third of what would eventually be 10 corpses and one skull found in the foul-smelling house and back yard. Cuyahoga County Coroner Dr. Frank Miller had called the scientist for help estimating when the victims died.

"You drop everything you're doing," said Keiper, an entomologist and the museum's director of science and

. "I know when I go to something like this, it's just going to be very horrific, very sad. But the second you get there, everyone has their game face on. It's like every other important job. You look past the emotion, you look past the normal human reaction to something that's horrifying like this. You do your job."

As one of two dozen or so U.S. entomologists with forensic experience, Keiper occasionally works as a law enforcement consultant. He uses his knowledge of the types of bugs that dead bodies attract, the timing of their arrival, and the rate of their reproduction and growth to judge how long a victim likely has been dead, among other things.

It's a fascinating, albeit gruesome, sideline that blends field biology with sleuthing. The concept of employing insects as clues in criminal cases has been around for hundreds of years, although forensic entomology has only emerged as a rigorous science discipline in the last few decades.

While criminal cases usually don't hinge on "bug evidence," knowing the approximate time of death may help police confirm or rule out a suspect.

"It's a tool in the toolbox," said Richard Merritt, a Michigan State University entomologist and former chairman of the American Board of Forensic Entomology. "It goes along with something else to verify that this person at this time was capable of doing something."

Because the Sowell case is an active investigation, Keiper can't say much about what he has found. He did recover insect samples from the bodies he examined at the crime scene and the morgue, and will be analyzing the evidence over the next few weeks.

"It's far too premature at this point to say if it's going to be useful or not," he said. "I hope the bug evidence contributes but . . . it will be some time before I know."

DSCN3940.JPGView full sizeCaption: Blowflies like this vividly colored green bottle fly can detect the smells of decay only minutes after death and arrive to lay eggs on the corpse.

When someone dies, nature provides many thousands of witnesses to the immediate aftermath. The first responders, far ahead of any cop or paramedic, are the flies, whose acute sense of smell alerts them to blood, urine, feces, and the distinctive gases produced as a body quickly begins to decay. They arrive within minutes of death, even if the corpse is indoors or somehow concealed.

"Flies can usually find a way through plastic, sleeping bags, paper bags," Merritt said. "There are some species of coffin flies that can actually burrow through the soil and lay their eggs in coffins. It's amazing."

In Northeast Ohio, about a dozen different types of flies and a comparable number of beetle species can inhabit decomposing bodies over the course of time.

Though it's upsetting for lay people to think about, a female fly's deposit of eggs on a corpse is a gift to investigators. It's like the first tick of a living stopwatch that will mark the passage of time from when insects first gain access to the remains.

Each stage of the development of a particular type of fly -- from wriggling maggot to dormant, shell-like pupa to the insect's emergence as an adult – takes a predictable number of hours or days.

The fly maggots, or larvae, provide the most precise detail because they get measurably bigger as time passes. By collecting the largest (and by inference oldest) larvae, then figuring out what fly species they represent, a forensic entomologist can, within limits, estimate what's called the post-mortem interval, or PMI: the period between death and the body's discovery.

There are a few twists, though, to how quickly a bug matures. Temperature is one variable. Because insects are cold-blooded, the cooler it is, the slower they grow. So forensic entomologists have to research weather records if the body was left outdoors, or check thermostat settings or ambient conditions if inside, and factor those into their PMI estimates.

Earlier this decade, Keiper worked on a case involving a strangled prostitute. He gave a probable time of death based on the size of the maggots collected from the body, but his estimate didn't match the rest of the evidence that investigators had.

What threw off Keiper's PMI calculation? Not temperature, but probably drugs.

"The victim had lot of cocaine in her system, which is a stimulant," he said. "You might think that would be a poison to insects feeding on the body, but in the literature there are tests that show that fly maggots feeding on tissue that has a stimulant like cocaine will grow more rapidly."

maggots10-19_1.JPGView full size The size and stage of development of maggots on a corpse helps forensic entomologists estimate the time between a victim's death and when the body is discovered. The maggots' metabolism can raise temperatures inside a mass like this to 100 degrees or more, which can accelerate their growth rate, so entomologists have to take that, as well as the air temperature at the crime scene into account.

Although he's not certain, Keiper believes the larger, cocaine-fueled maggots made it appear that the woman had been dead longer than she really had.

The lesson is that bug findings aren't necessarily ironclad, and that convincing criminal cases are built on multiple lines of corroborating evidence.

"That shows the power of a very complete investigation, like Dr. Miller has for the Sowell case," Keiper said.

One potential hitch in establishing the time of death of some of the victims in the Sowell investigation is that they appear to have been deceased for years, according to Miller.

As soft tissue disappears and the remains become mostly bones, the blowflies whose life cycles provide the most accurate information about time of death depart.

"I'd say the first 25 days we do the best," Merritt said.

However, because a definite progression of other types of bugs arrives after the flies leave, forensic entomologists can glean some timing information even from long-dead remains. Keiper has seen a skeleton exposed for two or three years that was still crawling with tiny checkered beetles.

"They tend to show up when you've gone beyond months of decomposition," Keiper said. "The older the body is, the rule of thumb is it's a more broad time-frame. I can't pinpoint a date, but I can add to the pile of evidence that suggests we're talking multiple years."

Sometimes the determination of when death occurred can dramatically impact a criminal case.

truscott-mug.gifView full sizeThe 1959 mug shot of 14-year-old Steven Truscott.

The final outcome of

depended heavily on bug evidence. In 1959, 14-year-old Steven Truscott was convicted of raping and strangling a 12-year-old classmate, Lynne Harper, and leaving her body in woods near the town of Clinton, Ontario.

Prosecutors used circumstantial evidence, especially a pathologist's testimony about the contents of Harper's stomach, to convince a jury that she died within minutes after witnesses last saw her riding with Truscott on his bike.

Truscott was sentenced to hang. His sentenced was later reduced to life imprisonment and his case helped abolish Canada's death penalty. He was eventually paroled but continued to insist he was innocent.

Nearly 50 years after Truscott's conviction, a Canadian appellate court reviewed the case. Merritt and another forensic entomologist examined photos and reports about the size of maggots on Harper's body – evidence that wasn't used at trial – and concluded that Harper likely was killed hours later than previously thought, after Truscott was home and in bed. Based largely on the scientists' testimony, the court overturned Truscott's conviction in 2007.

Forensic entomology "is not an exact science, let me tell you," Merritt said. "But on the other hand, the question is can you do better than anybody else. That's what insects can help with."

Keiper and others are working to refine the science and broaden its uses.

keiper-bear.jpgView full sizeDuring the summer of 2007, Joe Keiper studied insect activity on this black bear carcass in Geauga County.

Two years ago, he spent most of the summer studying what kinds of insects were attracted to the decaying carcass of a black bear he'd left in a grove of trees in Chardon. Keiper wants to apply his entomology skills to poaching cases, but needed to know if the types and timing of bugs that might be used to determine an animal's death were different than those in human investigations.

And this summer, working with Cleveland State University graduate student Krystal Hans, Keiper decided to test some conventional wisdom among forensic entomologists – namely, that the types of bugs found on a body can be a unique "signature," indicating whether it's been moved from one place to another.

Keiper and Hans were particularly interested in whether insects on a corpse differed between an urban and a rural setting, where a murderer might have a better chance of hiding the victim's remains. If "city" bugs could be detected on a body found in the country, cops would know it had been relocated.

For her master's thesis project, Hans got permission to place six 40-pound pig carcasses in various settings: two on a farm in eastern Cuyahoga County, two on the CSU campus in downtown Cleveland, and two that spent 24 hours on campus and then were moved to the farm.

The campus pigs were stashed near the university's outdoor tennis courts, which drew some curious questions from players who saw and smelled the experiment.

pupae.JPGView full sizeAs fly larvae mature, their form protective shells called pupae. Inside, they transform over a about six days into adult flies. When larvae are readying for the pupal stage, they move away from light, so forensic entomologists have to be careful to look for them beneath a body or in folds of clothing.

"I was very proud of Krystal," Keiper said. "She took the time to educate them. Although people wrinkled their noses about it, they thought it was morbidly fascinating."

Over two months, Hans and Keiper documented their pig corpse observations in a series of rather graphic blog posts. The bottom line? There was no insect indicator that a body had been moved, at least over short distances. The bugs devouring the city and country pigs were indistinguishable.

"These carrion flies and carrion beetles are so mobile that I just don't think this assumption holds water," Keiper said. "If there's a homicide in Cleveland and someone deposits the body in Indianapolis, you might be able to pick up a signature moving a distance like that. But you've got to move a large geographic distance. It's not as simple as moving a body 20 miles. Krystal's work is essentially busting a myth within the forensic entomology literature."

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