Cold case: Penn State pigs

In an open field near the mulch plant on Pennsylvania State University's State College campus, the body of a pig was slowly decaying in a wire cage, the molecules of putrescence collecting on an array of bristlelike suspended fibers.

While the dead animal had been outside for just two weeks, it was already reduced to a skeleton and a limp bag of empty skin. "The maggots work fast," noted chemist Daniel Sykes, who teaches at Penn State's school of forensics.

This is the fifth pig that Sykes and his students have laid to rest out there - part of an experiment to catalog the trace compounds released during decomposition. That, he said, might lead to new techniques for sniffing out homicide victims or identifying mass graves that hold victims of human-rights abuses.

The experiment is also part of a new Penn State forensics school seeking to bring scientific rigor to a beleaguered profession. Forensics isn't the neat and precise science so often portrayed on television. This year, the National Academy of Sciences exposed the shoddy standards accepted in most crime labs in almost every area of forensics except DNA.

Robert Shaler, a lead author on the report and director of the Penn State program, said that for decades forensics work was often done by technicians without training in scientific reasoning.

In some cases, that led to false convictions, later overturned by DNA evidence.

To address this problem, the American Academy of Forensic Sciences has been establishing uniform standards for college forensics programs. It recently granted accreditation to Penn State's program, placing it among 25 accredited programs in the country.

AAFS director Nancy Jackson said the number of students going into forensics programs was increasing but the number of graduates was leveling off, thanks to increasingly difficult math and science courses. "That sometimes dampens their enthusiasm," she said.

Students in the Penn State program not only learn to use equipment, they also build the devices to understand how they work, said Shaler, who had been director of forensic biology for the New York City medical examiner and leader of the effort to identify 9/11 victims using DNA. About 60 undergraduates are majoring in forensics. The program takes only 16 graduate students every year.

Earlier this month, the most recent pig used to map the scent of decomposition was used as part of a mock crime scene designed to help tomorrow's investigators think more scientifically.

The skin and bones were scattered around a field, and students were led out there without being told what they'd find, said Sykes, who had started the experiment with one of the program's graduate students, Sarah Jones.

For each pig, polymer-coated fibers suspended over the animal absorb trace compounds given off by the process of decay. Every day, Jones had been picking up some of the fibers, putting them on ice, and carrying them back to the lab to be analyzed.

Pigs are about the same size and body composition as humans, so they decay in roughly the same stages, Sykes said. It is possible to do similar experiments on human bodies - and some scientists have - but they can't generally start taking data at the moment of death.

This is important because bodies release a different mix of chemicals at different stages. Within the first six hours, the pigs give off organic compounds aptly called cadaverine and putrescine, and these or perhaps other similar gases start attracting insects.

The chemical-absorbing fibers cost thousands of dollars, but they might not be necessary in a field sensor. The purpose at this stage is just to develop a chemical profile, Sykes said, so students would know what to design a sensor to look for.

So far, they've been able to use the fibers to catalog hundreds of chemicals released by the pigs, an array that evolves day by day as the pigs decay. The pigs tend to decompose faster in hot, damp weather - something the researchers are also noting as they study pigs in different seasons.

Jones reported these results last month at a meeting of the American Chemical Society in Washington.

Finding victims of mass murder overseas remains another big challenge for forensic anthropologists, said Arpad Vass of the University of Tennessee, Knoxville. Right now dogs can be trained to find cadavers, relying on their ability to sniff out minute traces of telltale compounds.

"What dogs can do is unbelievable," Vass said, but they don't always want to work and they can communicate only with barking. Because the chemicals emitted by bodies can migrate, dogs sometimes can't home in on the exact spot. A device might be unable to outsniff a dog, Vass said, but there are circumstances where it might be more practical.

Still, he cautioned, to truly understand human decay, you need human bodies. His university is home to a "body farm" where he and other researchers can do experiments on donated human bodies.

So far, he said, his work has led to a catalog of 478 volatile chemicals given off by a decaying human. That in turn has led to a portable body detector, called Labrador, which he said can be used in conjunction with cadaver-sniffing dogs.

What the body farm can't do is study bodies in the first day or hours after death. "We're not hovering over them when they die," Vass said. There are consent issues and mourning issues that need to be worked through.

Still, Vass said, pigs give off a different set of fragrances. Humans emit fluorocarbons and other fluorinated compounds, for example, thanks to fluoride in our drinking water. Pigs do not.

"It's wonderful that more people are getting involved in this field," Vass said. "More research needs to be done." But he warns that researchers who work with pigs need to be aware of the pig/human differences. "Otherwise you've just got a pig detector."

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