PBS News Hour

JUDY WOODRUFF

So far this year, law enforcement has identified over 70 suspects using a new technique called genetic genealogy. This is the same tool that detectives in California last year used to identify the so-called Golden State Killer. In the first of two stories, William Brangham explains how this tool works and why it's raised serious privacy concerns. It begins with the murder of a young couple in Washington state, a case that became the first ever genetic genealogy case to go to trial. This is part of our Leading Edge series on science and technology.

WILLIAM BRANGHAM

In 1987, under the High Bridge in rural Washington state, a young man named Jay Cook was found murdered. His girlfriend, Tanya Van Cuylenborg, was found in the woods 60 miles away. She'd been raped and murdered. The only piece of evidence was semen from an unknown man found on Tanya's clothes. But it didn't match anyone, even after police DNA databases were developed in the following years. Eventually, the case went cold. But 18 years later, Snohomish County Detective James Scharf picked up the case. He turned to the public for new leads. JAMES SCHARF,

Snohomish County Police Detective

There is a green backpack that the person might have had, a black jacket and a Minolta camera.

WILLIAM BRANGHAM

But still nothing.

JAMES SCHARF

These were totally innocent kids, 20 and 18 years old. So this was a case that I really wanted to solve.

WILLIAM BRANGHAM

But the person who would eventually help crack the case wasn't in law enforcement at all. CeCe Moore is what's known as a genetic genealogist, someone who helps people trace their family ancestry. CECE MOORE, Chief Genetic Genealogist,

Parabon NanoLabs

By about 2012, I think it was starting to kind of bubble to the surface with a few of us that what we're doing could have law enforcement applications. But it wasn't time yet. The databases were too small.

WILLIAM BRANGHAM

But that was all about to change when commercial DNA testing suddenly went mainstream.

WOMAN

Don't just give a gift. Give them AncestryDNA.

WILLIAM BRANGHAM

DNA testing services, like Ancestry.com and 23andMe, have exploded in popularity. Its estimated that more than 26 million people have now used companies like this. The process of testing your DNA is actually pretty simple. You order the kit online. These each cost about $100 each. And then you just spit some saliva into a tube like this, you mail it in, and, in a few weeks, you get your DNA reports. As millions of people started getting their DNA results, many of them copied their data into other public Web sites, so they could better find distant family members. But CeCe Moore realized this wealth of information could also be used to help solve cold cases.

CECE MOORE

We have two matches at the top of the list that are both sharing about 3 percent of their DNA with the unknown suspect.

WILLIAM BRANGHAM

She demonstrated how she did it in the Cook/Van Cuylenborg case. She took the unknown suspect's DNA from that semen sample and compared it to DNA results in the databases. She found two partial matches, people who were likely the killer's two second cousins.

CECE MOORE

So, if you share 3 percent of your DNA with someone, then you are most likely second cousins, which means you share great-grandparents. So I am going to build these trees back to great-grandparents.

WILLIAM BRANGHAM

From there, she went back in time, up the family tree, up to the great-grandparents of those cousins.

CECE MOORE

We should find the common ancestor at this level somewhere with the unknown subject.

WILLIAM BRANGHAM

From there, moving down the family tree, she searched public documents and obituaries to find where these two families converged. This family would likely be the suspect's immediate family his, parents and siblings.

CECE MOORE

But, from the DNA, we know it's a male, and these are daughters.

WILLIAM BRANGHAM

This was how she identified the likely culprit.

CECE MOORE

This allows me to zero in on just this one male as the potential suspect. It was a very odd moment to be looking at the name of the person I believed to be a killer, and know that I was the only person in the world who probably knew what he had done, other than himself. But this was a very heavy discovery. And I just wanted to quickly get that name to Detective Scharf and get that off my shoulders.

WILLIAM BRANGHAM

For Detective Scharf, this was a huge lead, but not enough to make an arrest. He'd need actual DNA from the suspect to know for sure. And so a coffee cup discarded by the suspect was collected by the police and tested. When the results came back, it was a match.

JAMES SCHARF

And I got tears in my eyes, and then I screamed that, yes, we finally got this case solved. It was just such a wonderful feeling.

MAN

Yesterday, we took into custody a 55-year-old SeaTac man who is suspected of the 1987 murders of Jay Cook and Tanya Van Cuylenborg.

WILLIAM BRANGHAM

This summer, 56-year-old William Earl Talbott II went on trial for the murder of Jay cook and Tanya Van Cuylenborg. Talbott pled not guilty, and never took the stand. His lawyers argued that the presence of Talbott's semen at the crime scene could have been from consensual sex. JON SCOTT,

Attorney For William Earl Talbott II

There is evidence consistent with sexual intercourse, but not injuries associated with assault. She wasn't bruised or battered. There wasn't evidence of sexual assault.

WILLIAM BRANGHAM

The only definitive thing linking Talbott to the crime was this DNA match. After two days of deliberation, the jury convicted Talbott of first-degree murder for both Cook and Van Cuylenborg. He was sentenced to life in prison. This was the first ever trial and conviction on a case cracked open by genetic genealogy.

JAMES SCHARF

Without genetic genealogy, this case never would have been solved. CeCe Moore did in two hours what 20 or 30 cops couldn't do in 30 years of working on this case. That's how powerful genetic genealogy is in solving crimes.

WILLIAM BRANGHAM

In our next story, we will explore the deeper privacy implications of this technique and why some are so concerned about this new crime-fighting tool. For the "PBS NewsHour," I'm William Brangham.