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caption: Laura Baanstra, center, testifies at the trial of William Earl Talbott II on Friday, June 14. Talbott has been charged with killing her brother, Jay Cook, and his girlfriend Tanya van Cuylenborg in November of 1987. In the foreground: May Robson, left, Tanya's best friend, and John van Cuylenborg, Tanya's older brother, watch Baanstra's testimony.
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Laura Baanstra, center, testifies at the trial of William Earl Talbott II on Friday, June 14. Talbott has been charged with killing her brother, Jay Cook, and his girlfriend Tanya van Cuylenborg in November of 1987. In the foreground: May Robson, left, Tanya's best friend, and John van Cuylenborg, Tanya's older brother, watch Baanstra's testimony.
Credit: Andrew Bronson / Everett Herald

Genealogy helped solve this cold case. But prosecutors are downplaying it

The trial of William Talbott II is underway in Snohomish County. Police found him using genetic genealogy.

Siblings of Jay Cook and Tanya van Cuylenborg testified Friday afternoon at the trial of the man who police say killed the young couple.

Laura Baanstra described her brother Jay as sweet, generous and kind. She recalled how he took her out for high tea with money he’d made working on a fishing boat.

“He made sure we had our pinkies up," Baanstra testified.

Talbott was arrested based on a DNA match. Detectives found DNA at two scenes related to the murders, but weren't able to identify it for more than 30 years.

Last year, the Snohomish County Sheriff's office partnered with a company that helped them run the DNA through a public DNA database. They found matches to two relatives of the DNA's owner. They then created a reverse family tree that led them to Talbott.

The technique is a new one for law enforcement. Talbott is the first person to go on trial based on this kind of identification, although it has been used to ID suspects or perpetrators in dozens of cases.

Those cases include the Golden State Killer case. Suspect Joseph DeAngelo is awaiting trial for a suspected 13 murders in that case.

Still, in opening statements, Deputy Prosecuting Attorney Justin Harleman downplayed the precedent-setting nature of the case.

“This process gave law enforcement a tip. A tip just like any other tip that they would follow up on, that they would investigate themselves and determine that William Talbott was, indeed, the perpetrator, “Harleman said.

Cook and van Cuylenborg went missing in November 1987, while on an overnight trip to Seattle. Days later, their bodies were found 70 miles apart.

20-year-old Cook was found under a bridge in Woodinville. He’d been beaten and strangled.

Van Cuylenborg was 18. She was found shot near a culvert in a rural area of Skagit County. Prosecutors say she was raped, and semen from her body matched to Talbott.

Talbott has pleaded not guilty. He fought a motion from his attorney that delayed the trial by a week, telling a judge his life had been put on hold for a crime he didn't commit.

Appearing in Snohomish County Superior court Friday in a grey shirt and red tie, Talbott stared intently at the State's witnesses.

John van Cuylenborg, Tanya’s older brother, told the court how he and his father William drove to Washington State looking for clues after Tanya went missing.

When they called home that night, they discovered a body had been found that police suspected was Tanya's. They then traveled to a Mount Vernon funeral home to identify her body.

In opening statements, defense attorney Jon Scott told jurors prosecutors really don’t know what happened.

“The evidence doesn’t tell us anything," Scott told jurors. "We know at some point during that time, they were killed. We know the means, but not the context."

The trial is expected to last three weeks.