Video: DNA now used to track animals

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When Ryan Armstrong was only seven years old, a loose dog nearly tore off his thumb and punctured his chest.

"I was very scared. I thought I was going to die right there," he said.

Ryan's dad worked for years to find the dog, but got nowhere, until experts suggested comparing DNA on the jacket Ryan was wearing to saliva from two dogs in the area.

"If you saw your child laying there all tore up, was this close to death, I think now you need to know who did it, who's responsible for this," said Jeff Armstrong.

"Anything that can be done for human DNA could theoretically be done for animal DNA. They don't have to have a suspicion about what animal was responsible for something, they can absolutely prove it," said Dr. Janice Sojka, who teaches animal forensics at Purdue University.

She says DNA samples can be taken from animal hair, drool, and even chew toys. Then you send the samples to a specialized veterinary genetics lab like the one at U.C. Davis.

"There's a huge range of sample types and samples that come into the laboratory," said Elizabeth Wictum, Veterinary Genetics Lab, University of California Davis.

And the samples can help solve stolen dog cases and other crimes.

Marylin Christian used it after her cat Cody was killed in her back yard. She thought the neighbor's dog may have done it, but she couldn't prove it.

"It was the vet that suggested using the DNA," she said.

The lab confirmed her suspicions, telling her there is only a 1- in 67-million chance that the hairs belong to a dog other than her neighbor's.

"To me, this proved beyond a reasonable doubt that it was in fact that dog,” said Marylin.

Shortly after Marylin got the results, the animal's owner moved away.

Ryan and his dad also found closure with the DNA results. The dog's owner was arrested and charged with having a dangerous dog.

DNA testing ranges from $500 to $1,000.