EVERETT, Wash. — Authorities in Washington state on Wednesday released composite sketches based on DNA evidence of a suspect in an unsolved, 30-year-old double slaying of a young Canadian couple.

Tanya Van Cuylenborg, 18, and Jay Cook, 20, of British Columbia were found dead in two separate locations after they failed to return home from a visit to the Seattle area in 1987.

DNA evidence collected during the investigation did not match profiles in any databases, but investigators with the Snohomish County and Skagit County sheriff’s departments released three composite sketches of a Caucasian male shown in his 20s, 40s and 60s.

The sketches were based on DNA phenotyping, the process of predicting physical appearance and ancestry from unidentified DNA evidence.

Snohomish County Sheriff Ty Trenary says he hope the sketches will help identify a suspect.

“Jay and Tanya were brutally murdered and, more than three decades later, their killer has yet to be brought to justice,” Trenary said in a statement.

Van Cuylenborg and Cook left their Saanich, British Columbia, homes on Nov. 18, 1987, for an overnight trip to Seattle. They were driving a brown 1977 Ford van. The purpose of the trip was to buy furnace parts for Cook’s family business.

When the couple failed to return home, their families filed a missing persons report.

On Nov. 24, a man walking on an isolated road south of Bellingham, Washington, discovered Van Cuylenborg’s body. She had been sexually assaulted, bound with plastic ties and shot in the head.

Cook’s battered body was found the next day about 2 miles (3.2 kilometers) south of Monroe, Washington. The two locations where the bodies were found are about 75 miles (120 kilometers) apart.

The police were able to obtain the suspect’s DNA from the van, although there has been no match on any criminal database.

Several private companies offer phenotyping services to law enforcement to create sketches of suspects or victims when decomposed remains are found. The process looks for markers inside of a DNA sample known to be linked to certain traits. Police in at least 22 states have released suspect sketches generated through phenotyping.

The American Civil Liberties Union has said not enough is known about the link between genes and facial features to rely on the technology to produce a suspect.