This computer generated composite image based on DNA evidence released by the Snohomish County Sheriff's Office shows a white man with fair hair and green or hazel eyes, at age 25, left to right, 45 and 65, traits that investigators say are connected to the DNA of the person they believe killed 18-year-old Tanya Van Cuylenborg and 20-year-old Jay Cook. Police in Washington state have released images of a man created through groundbreaking DNA technology that they say could help solve the murders of a young British Columbia couple more than 30 years ago. THE CANADIAN PRESS/HO, Snohomish County Sheriff's Office *MANDATORY CREDIT*

EVERETT, Wash. - Police in Washington state have released images of a man created through groundbreaking DNA technology that they say could help solve the murders of a young British Columbia couple more than 30 years ago.

The composite images released by the Snohomish County Sheriff's Office show a Caucasian man with fair hair and green or hazel eyes, traits that investigators said are connected to the DNA of the person they think killed Tanya Van Cuylenborg, 18, and Jay Cook, 20.

"We believe that someone knows who our person of interest is," investigations Capt. Jim Miller said at a news conference on Wednesday. "Maybe you were too afraid to come forward at the time or you thought someone else already had. Now is the time to share what you may have seen or heard and bring closure to this crime."

The high school sweethearts from Saanich, B.C., were on their way to Seattle to pick up furnace parts for Cook's father when they disappeared in November 1987.

Their bodies were found in separate locations outside the city days later. Van Cuylenborg had been restrained with zip ties, sexually assaulted and shot in the back of the head. Cook had been strangled and zip ties were found near his body.

Forensic evidence found at the crime scenes has been tested against databases in both the United States and Canada over the years, but investigators have never found a match.

Recently, they sent a sample to a lab in Virginia for DNA phenotyping, a process that looks at specific codes to predict a person's appearance, including eye, skin and hair colour, facial features and ancestry.

The technology cannot indicate traits like age or body weight, but Parabon NanoLabs, the company that did the analysis, predicts the suspect is a man of northern European ancestry, with very fair skin and possible freckles, with light brown hair and could be balding.

The sheriff's office released three images showing what the suspect may have looked like at 25, 45 and 65 years old.

Miller noted there may be differences between the real-life killer and the images, but said the technology has been used to help solve other cases.

"It's not 100 per cent guaranteed. It's not a photograph. It's a composite," he said.

Investigators have never given up on solving the case and the new images renew their optimism, said Det. Jim Scharf.

"Hopefully someone out there knows an individual that looks similar to this that was in the area at the time and capable of committing this crime. All we need to do is get a sample of his DNA to match and identify him," he said.

"The smallest detail could end up being the lead that we need to solving this case."

Cook's sister, Laura Baanstra, still hadn't looked at the images when police unveiled them Wednesday.

"That could be the likeness of the person that killed my brother. That's tough," she said.

Baanstra said the last time she saw her brother was as he was getting ready to leave for Seattle. He hadn't had anything to eat and asked for a bite of her sandwich. Reluctantly, she gave him half before standing in the window and waving goodbye, she said with a small smile.

"When your brother or sister, daughter or loved one, walks out the door, you have no way to know that you will never see them again."

Baanstra pleaded for anyone with information about her brother's murder to call police, even if they only have "an inkling of an idea."

"If these new pictures that this amazing new technology created triggers a memory you had, perhaps of someone who said something odd that lived in or near the Snohomish area or even Vancouver in late 1987, please, for the sake of my brother, Jay, Tanya and all of our families, call it in," she said.

A C$50,000 reward for information leading to a DNA match has been offered through the end of December.

— By Gemma Karstens-Smith in Vancouver

News from © The Canadian Press, 2018