Some of the students in Bob Kimsey's forensic entomology course are having a difficult time watching maggots crawl over the decomposing body of an animal in a field just west of the campus.

Working together in small groups, the students listen intently to their instructor as he carefully examines the pig's body, pointing to different areas where insects typically enter and exit rotting carcasses. With that, Kimsey leans down and turns over the animal, revealing a new, bustling mass of insect activity beneath -- with each busy insect telling its own story about the pig's death.

For years now, homicide detectives have been able to determine the cause and manner of someone's death by analyzing crime scene gunpowder residue or blood spatter or by collecting ballistics measurements and other scientific data. Now law enforcement agencies are seeing the value insects play in forensic science.

"Law enforcement has come to realize more frequently that there is a lot of information (insects can help reveal) regarding when a person died, where they died and, to a much lesser extent, how they died," said Kimsey, an assistant adjunct professor in entomology.

Forensic entomology is a science that has proven to be instrumental in helping to solve puzzling murder cases, said Yolo County Deputy Coroner Mary Koompin-Williams. "This specialty is now getting recognition in courtrooms around the United States," she said.

Kimsey teaches undergraduate classes that introduce students to the field of forensic entomology. Each spring quarter 30 upper-division students learn about the biology, succession and developmental cycles of insects that invade corpses. The class is popular in part, he said, because he takes students to the field, where they analyze, collect and document insect movement on animal carcasses.

The growing discipline of forensic entomology also will be spotlighted this summer as the campus hosts the North American Forensic Entomology Confer-ence. Some 150 academics, students, forensic pathologists, law-enforcement officials and lawyers are expected to gather for the second annual event, set for July 21-23. Experts will share information -- as well as their professional experiences -- and take part in forensic arthropod-identification workshops and demonstrations.

A mix of know-how and nerve

For their field work, students in Kimsey's class have come prepared with gloves, tweezers and glass tubes so they can take samples of the many types of insects commonly found on and around dead bodies. Collecting insect eggs from the animal's skin might be tedious -- or even nauseating -- work to some, Kimsey said. But it's crucial in determining time of death, since the life cycle of insects, like decomposition itself, is a predictable biological process.

Kimsey said forensic entomologists factor in the size of maggots, their developmental stages and the temperature of the infestation. "If you know what stage the maggot is in and you know the temperature of the egg mass, then you can determine the age of the maggot, which provides insect forensics specialists with an approximation of how long the corpse has been dead," he said.

Knife or bullet wounds also can speed decomposition, because holes that penetrate skin, muscle, organs and other body parts provide an easier entry point for insects. "You increase the rate at which insects can actually invade and destroy the remains when there is an opening in the skin," Kimsey said. "A gunshot wound that goes through the abdomen is likely to penetrate the intestines, opening the contents to infestation."

Dozens of species and families of insects are commonly found on dead bodies, including mites, which occur under a body in the soil during later stages of decay, gnats, beetles and hundreds of types of flies. After death, a succession of fungi and bacteria also will colonize the body. And fluid loss will lead to the disappearance of certain insects and the prevalence of others.

Hands-on with human corpses

Kimsey's students have a chance to further put their skills to the test as they spend a day at the Sacramento County Coroner's office, where they investigate the time of death of decomposing human corpses.

The trip to the coroner's office is important for a number of reasons, Kimsey said. "We teach them a lot in the laboratory on campus -- like how to make the collections, what to look for, how to make the identifications and how to make the calculations. But it doesn't really make for a whole lot of implied sense until you have done it on a real case. Being in the presence of a decomposing body and exercising the stability to carry out the research that is needed to help law enforcement is critical in the maturation of our students," he said.

The students agree. "Coming here to the coroner's office and working with the deceased is unique because it gives us hands-on experience that you wouldn't get from just looking at a slide show on the screen in the classroom or reading about case studies from a textbook," said Matt Fossen, a graduate student in entomology. "I think the experience here in the autopsy room gives us more a feeling of what is really going on and how to execute insect science on human decomposition."

Kimsey said forensic entomology is still in its infancy and more understanding of insect behavior is needed. Fewer than 100 forensic entomologists exist in the world, he said, noting that many of these insect experts are associated with universities. There are still just a handful who actively work with law enforcement on death scene investigations.

Beyond forensic pathology

Currently, forensic pathologists are very accurate in determining time of death within a three-day window, Kimsey said. But making determinations about corpses that remain outdoors for longer periods of time is more challenging. That's where insect forensic specialists become helpful -- by analyzing developmental stages of insect activity.

Koompin-Williams added that insect activity can be helpful to a trained entomologist, "who can establish if any illicit substances are in the remains."

Poisons and other drugs that could be the cause of death or offer leads in an investigation, such as cocaine, heroin or antidepressants, are sometimes detectable in insect samples longer than they are in samples from a dead body. Ingestion of certain drugs and poisons also can influence the distribution of insects throughout the body. Such compounds also alter the development of insects in predictable ways, Kimsey said.

Forensic entomology also has been used in cases related to drug trafficking. Investigators can look at the biology and type of insect species found with the drugs, and, since many insects are specific to certain locations in the world, that can often say something about the drugs' place of origin.

Investigators also might look at the specific species of arthropod to get a fix on the place of death -- some are more abundant in wooded areas, others along seashores; some in shade; others in bright areas; some rural, others more urban.

"In addition to time of death, bugs can say something about the place of the death and whether a body has been moved. And if the type of insect found in a body wouldn't normally have access to the body in that location, a detective also can infer that the body was perhaps moved," noted Kimsey.

So even if dead men don't tell tales, the creeping, crawling evidence around them certainly can.