Animal DNA Becoming Crucial CSI Clue

Maryann Mott
for National Geographic News

December 12, 2006

A triple murderer is spending life in prison, thanks to a dog's DNA.

In the fall of 2000, Phillip Stroud and three accomplices were burglarizing an upscale home in Lakeville, Indiana, when they realized that three construction workers were in a barn on the property.

To cover the burglars' tracks, then-21-year-old Stroud shot each worker in the head, according to court papers.

In statements later given to police, Stroud claimed he was only a lookout and that he never left the car.

But his involvement in the homicide became clearer to investigators when DNA from dog feces found outside the house matched excrement on his sneakers.

It ended up being a key piece of evidence. Stroud was ultimately convicted of murder and is serving life without parole.

The crime is just one of a small but growing number of cases where animal DNA evidence is being used to help identify and convict killers, rapists, and thieves.

Denver District Attorney Mitch Morrissey, an expert in DNA technology, says as long as people share their lives with pets, animal DNA is bound to play an increasing role in crime scene investigations.

"Unfortunately our homes are crime scenes, and animals are witnesses that usually can't tell you much about what happened. But if you find their DNA it can be pretty important evidence," he said.

CSI Animals

The Veterinary Genetics Laboratory at the University of California's School of Veterinary Medicine in Davis is one of the leading animal forensic laboratories in the country.

The lab's forensic branch was formed seven years ago because of a growing number of requests for service by law enforcement agencies, according to the lab's director, Elizabeth Wictum.

Think of it as the CSI of the animal world.

Each day, five forensic scientists toil over cases from around the world, including one from Britain's famed Scotland Yard, where they analyzed dog blood found at a murder scene.

Last year the lab handled about 90 criminal cases. Wictum says most involve tying biological evidence to a pet that's owned either by the victim or suspect.

In an older case involving a sexual assault in Iowa, for example, the victim's dog relieved itself on the man's pickup truck during the attack. The lab was able to match the dog's DNA to a sample taken from the vehicle, helping prosecutors win the case.

When a match is made, Wictum says, it has a powerful effect.

"Often times when you get the DNA evidence people will work out a plea deal, because they know they can't fight it," she said.

If a case does wind up in court, the lab's findings are rarely challenged, she added.

"I think it's because the human DNA evidence has been so well documented and it's so universally accepted now that we tend to be accepted also," Wictum noted.

"It's the same technology, the same type of testing, and the same type of results."

In addition to violent crimes, the lab also analyzes genetic material for pet custody disputes, deadly dog maulings, and even cattle rustling.

Wictum said her team deals with many cases involving cowboys who swipe cattle to make a quick profit.

"It's a booming business," Wictum said, rattling off several western states where the crime often occurs. "As beef prices go up, cattle-rustling goes up."

Cats, Plants Fight Crime

Investigators normally don't look for or collect animal DNA from crime scenes, but legal experts say more detectives and lawyers are starting to recognize its importance.

Morrissey, Denver's district attorney, says he has personally requested that blood or hair samples be taken from pets.

During one case, he said, eight cats lived inside the home of a suspected serial murderer. Police had already found two women buried next to the house, and the suspect claimed he had dumped three more in remote parts of state.

Knowing that cat hair clings to everything and would likely turn up on the bodies, Morrissey instructed police investigators to get samples from each feline.

"There was a time in this business you probably would have heard the laughing from wherever you are when I brought it up," said Morrissey, a 25-year veteran of the legal profession. "But that did not happen."

Plant DNA is also playing a role in crime solving, says Matt Redle, prosecutor for Sheridan County, Wyoming.

In the 1992 murder of an Arizona woman, DNA from seed pods found in the suspect's truck matched the DNA from a palo verde tree at the crime scene. That evidence, in part, led to a first-degree murder conviction.

"The only limitation to use [of nonhuman DNA in investigations] is really the imagination of the investigators involved," Redle said.

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