'Abandoned' DNA Solving Cold Cases

Aug. 24, 2007— -- Seattle, 1982. An unknown suspect murdered a 13-year-old girl. The investigation went cold for 20 years with no leads -- until officers tricked the suspect into mailing them a letter.

They wanted his saliva, loaded with his DNA, on the envelope.

Police cracked the case, using the genetic imprint from the suspect, John Athan -- evidence he unwittingly sent them through the mail.

DNA -- it's a key clue in TV dramas, in addition to helping crack old cases in the real world. Today, all over the country, detectives are re-examining evidence collected at the time of the crime, comparing it to so-called "abandoned" DNA, like the saliva on Athan's letter.

Detectives are solving crimes using sweat collected from a steering wheel, or saliva from a discarded cigarette butt. In a Detroit case, it was spit on a leftover cinnamon roll that sent a man to jail for car theft.

"People leave parts of themselves all over all of the time," said Seattle Police homicide detective Nathan James. "DNA is like fingerprints, only better. It is just more precise than fingerprints. At this point it is more reliable than fingerprints."

In Buffalo, N.Y., investigators solved a triple homicide after police trailed a suspect to a restaurant. When Altemio Sanchez finished dinner, they scooped up his dirty dishes.

"We got the DNA from him off of a coffee cup," said Erie County, N.Y., district attorney Frank Clark. "That's how we got the sample, the known sample that we could apply against the DNA found from our homicide victims."

Clark told ABC News that investigators look to find DNA in every imaginable place. "I mean, we're looking at cigarette butts, we're looking at chewing gum. We're looking at shirt collars. We're looking at the insides of gloves. Everything you used to dust for fingerprints for, now you look for DNA."

If a suspect drinks from a cup and tosses it away, detectives like Dennis Delano of the Buffalo Police Department can easily work with evidence left behind. "Anytime that you drink out of something, you will leave biological fluid. They can get a full DNA profile from [a] cup," he said.