Last week, William Earl Talbott II was arrested for the murder of Jay Cook, 20, and Tanya Van Cuylenborg, 18. A murder that happened over three decades ago.

The crime had gone unsolved since 1987, but the growing popularity of genealogy websites has allowed experts to use previously discarded DNA evidence to track down the suspected killer. The exact same technique was used to identify Joseph James DeAngelo, 72, better known as the alleged Golden State Killer, just three weeks ago.

Cook and Van Cuylenborg were a young couple from Canada who had been holidaying in Washington State when they were brutally attacked. Van Cuylenborg’s body was discovered dumped in a ditch in Skagit County woods, while Cook's body was found at a separate location a little later. 

Despite some promising leads, including one individual who sent letters to the victims' family actually claiming to be the killer, police were not able to find the man who did it. Now, thanks to the exciting new field of genetic genealogy, criminal investigators are getting a second chance to solve this and other cold cases. 

So, how did they do it?

 

DNA taken from the crime scene was sent to a public genealogy site called GEDmatch, which flagged up a second cousin and a half-first cousin once removed. Both had voluntarily uploaded their DNA to a site like AncestryDNA or 23andMe.

CeCe Moore, a genetic genealogist, then used publically available family data, census data, social media, and newspaper archives to build a family tree. Conveniently, one of the suspect's relatives was on the mother's side and the other on the father's side, which made this case a particularly straightforward one to piece together. 

“This led me to two descendants of the great-grandparents of the original matches who married, thus tying the two families together,” Moore said, the New York Times reports. 

Following the family tree, they identified a Mr Talbott, who was his parents' only son and 24 at the time of the murders. A little detective work revealed he had been staying at his parents' home, roughly 11 kilometers (7 miles) away from where Cook's body had been found. 

Investigators followed Talbott, now 55, for several days and were able to collect a discarded cup carrying DNA. (He was working as a truck driver at the time, which just so happens to be one of the most common professions among serial killers.) Lab tests confirmed it was indeed a match. 

Talbott has pleaded not guilty and is currently sitting on a $2 million bail.

Many more previously thought unsolvable cases may be settled in the coming months, according to Parabon NanoLabs, a DNA tech company involved in the investigation, including the Zodiac Killer.

A spokesperson from the company recently told BuzzFeed it has uploaded DNA from some 100 crime scenes, of which 20 or so have come up with matches of a third cousin or closer.