A man charged with murder in the 1987 killings of a young Canadian couple is facing trial in Washington state beginning this week, but the case won't challenge the new investigative technique authorities used to link him to the crime.

William Earl Talbott II is one of dozens of men authorities have arrested for old, unsolved crimes in the past year using genetic genealogy. The practice involves identifying suspects by entering crime-scene DNA profiles into public databases that people have used for years to fill out their family trees.

Privacy advocates have expressed concerns about whether it violates the rights of suspects and whether its use by law enforcement should be restricted. But Talbott's attorneys say how detectives found him is irrelevant to their defense to charges that he killed 18-year-old Tanya Van Cuylenborg and her boyfriend, 20-year-old Jay Cook.

Instead, they argue that he's innocent, and that the discovery of his DNA — which investigators said was on her pants, vagina and rectum — doesn't make him a murderer.

"The police used this as nothing more than any other tip, which they followed up with traditional investigative techniques," defense lawyer Rachel Forde said. "DNA on the hem of one of the victim's pants doesn't tell you who killed her and why."

Van Cuylenborg and Cook disappeared in November 1987 during what was supposed to be an overnight trip from their hometown of Saanich, British Columbia, to Seattle, to pick up furnace parts for Cook's father's business. After a frantic week for their families, Van Cuylenborg's body was found down an embankment in rural Skagit County, north of Seattle. She had been shot in the back of the head.

Hunters found Cook dead two days later next to a bridge over the Snoqualmie River in Monroe — about 60 miles (95 km) from where his girlfriend was discovered. He had been strangled with twine and dog leashes.

Over the next three decades, detectives investigated hundreds of leads, to no avail. But in 2017, Snohomish County sheriff's detective Jim Scharf learned about Parabon Labs in Reston, Virginia, which was using a new DNA processing method to extract more information from samples. CeCe Moore, a genealogist there who is known for her work on the public television series "Finding Your Roots," was using the more robust genetic profiles to find distant relatives using the public genealogy database GEDmatch.

In 2018, investigators in California used this technique to arrest and charge a man with being the sadistic attacker known as the Golden State killer who killed 13 people and raped nearly 50 women during the 1970s and 1980s.

With a sample from Van Cuylenborg's pants, which were discovered in the couple's van in Bellingham, Washington, after their deaths, Moore built a family tree and determined that the source must be a male child of William and Patricia Talbott. William Talbott II, now 56, was their only son. He was 24 at the time of the killings and lived near where Cook's body was found.

Detectives tailed Talbott, a truck driver, and saw him discard a coffee cup. They tested the DNA left behind, confirming it matched that found on the pants. They say he also matched a palm print from the rear door of the couple's van.

Talbott's friends were stunned. Several wrote the court, describing him as kind, gentle and helpful.

Opening statements in the case are expected Thursday in Snohomish County Superior Court, with the trial scheduled to last four weeks. In an agreement reached Tuesday, prosecutors and defense attorneys agreed the jury did not need to hear testimony from anyone at the genealogy lab. Instead, the detective will testify about how Talbott came under suspicion.

Among the privacy issues raised by the investigation method is that the technology is so powerful that even without a warrant, police can identify people based on the participation of distant relatives in the public databases.

Mary D. Fan, a University of Washington Law School professor and former federal prosecutor, said the use of genetic genealogy in criminal investigations may have broad support among the public when it's being used to arrest serial killers or to solve other cold homicides. It's less clear that support would hold if authorities used it to identify shoplifters or other low-level suspects.

Any restrictions on the technology's use would best come from lawmakers, she said.

"If you're going to take away the ability of people to participate in these services or to make their data available to police, or if you're going to restrict the ability of the companies to offer these services, that's best left for the legislative branch," Fan said.

GEDmatch itself has recently changed its policy to require people to opt-in if they want law enforcement to have access to their DNA profile. That closed off more than a million profiles to law enforcement. More than 50,000 users have agreed to share their information — a figure that the company says is growing.

For John Van Cuylenborg, the victim's brother, a lawyer in Victoria, seeing serious crimes solved is worth the potential privacy cost. He remembers his sister as a compassionate young woman and called having to identify her body "the darkest of days."

"For the computing power and DNA technology to advance together to make this kind of thing possible, it was fantastic," he said.