EVERETT (AP) — Jurors in Everett on Friday heard about the mysterious final days of a young Canadian couple killed in 1987 — as well as the novel method authorities used to finally make an arrest three decades later.

William Talbott was arrested last year and charged with aggravated murder, after authorities said they used genetic genealogy to identify him as the person who left his DNA on the clothing of one of the victims. 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.

In his opening statement Friday at Talbott’s trial, attorney Jon Scott noted there’s little or no evidence about who 18-year-old Tanya Van Cuylenborg and her boyfriend, 20-year-old Jay Cook, were with or what they did in the days before they were found dead in Washington state.

Talbott was arrested last year.

Scott’s opening statement did not offer any theory about how the DNA wound up on the woman’s clothing.