Catching criminals with genetic tests is not an invasion of privacy

Tanya Van Cuylenborg’s killer went free for decades until DNA evidence led to his arrest in Washington State. The young Victoria woman’s boyfriend was also killed but no one has been arrested so far.

image: Canadian Forensics Inc.

The cold case was solved with the help of a genetic genealogist, CeCe Moore, in just eight hours. She reluctantly helped with the investigation:

“It’s something I declined to do for a very long time. I was concerned about informed consent, about people in the genetic genealogy databases having their DNA used for a purpose they had not consented to and were not aware was a possibility (Globe and Mail, June 8, 2018)”

Moore’s reluctance had nothing to do with gathering evidence at a crime scene. If perpetrators leave evidence, such as fingerprints, at a crime scene consent is not required.

Nor does DNA evidence gathered in a public place require permission. Police don’t even need a search warrant to take a discarded coffee cup from the trash. That’s how DNA was gathered from the alleged killer and matched to DNA he left behind at the crime scene.

Moore’s reluctance had to do with the fact that the consent of dozens of people related to the alleged killer had not been given. His relatives wouldn’t even have necessarily known about the investigation.

The comparison of DNA to fingerprints is useful because it reveals the stark difference. A fingerprint indentifies one, and only one, person. DNA indentifies one person -and all of that person’s relatives.

An obvious question to ask is: “why did it take police 31 years to match the alleged killer’s DNA with that at the crime scene?” It seems like a simple thing to do until you realize that the number of discarded coffee cups, or whatever, that would have to be analyzed would be in the millions –a logistically improbable task.

That’s when an open-source genealogy database called GEDMatch came in handy. The original purpose of the database was not to catch criminals but rather to help “amateur and professional researchers and genealogists.” By May, 2018, the database had 929,000 genetic profiles.

Detectives uploaded a DNA sample from the crime scene to GEDMatch. From there, they identified ancestors and relatives of their suspect. With the help of Moore they built a family tree, incorporating marriage records and other information, and worked their way backward to find a potential suspect. It was only then that they knew whose discarded coffee cup to check.

Civil libertarians worry about the misuse of the technology by the police. However, while police need a court order to access some private sector databases like and 23andMe, GEDMatch is open-source.

Civil libertarians worry about the invasion of privacy. It’s also true that in giving GEDMatch permission to share my genetic information, I might be giving access to my third cousin Fred’s genetic information. And that hapless Fred may unknowingly be part of a police investigation without his consent.

Despite all those reservations, the family tree of suspects should be open to investigation as long as the investigation doesn’t incriminate those family members in any way –the target of the investigation must be clearly stated with no fishing allowed.