Norwegian Murder Case: 28 Years, DNA Evidence, and a Wrongful Conviction

On the Norwegian island of Karmøy in 1995, 17-year-old Birgitte Tengs was found raped and murdered. The crime would remain unsolved for nearly three decades, until advances in DNA technology and international genetic analysis reignited the investigation—only to expose profound weaknesses in how courts evaluate forensic evidence.

When Birgitte was killed, DNA technology was insufficient to identify her attacker with certainty. However, blood traces on her tights contained Y-chromosome DNA from the perpetrator. This evidence would sit in storage for years, waiting for science to catch up.

In autumn 2021, Norwegian police reached out to Mikkel Meyer Andersen, a Danish genetic expert, to assess the rarity of a Y-STR (Y-chromosome STR) profile recovered from the victim's clothing. Over subsequent months, four international laboratories conducted extensive analysis using advanced techniques including massively parallel sequencing. Genealogy studies traced the DNA profile across Norway and beyond. By early 2023, investigators believed they had their man: Johnny Vassbakk.

In February 2023, Vassbakk was convicted of rape and murder. The Y-STR evidence had proven decisive—described in Norwegian as "tungen på vægtskålen," the tongue on the scales of justice. Yet from the beginning, there were complications. Y-STR evidence alone cannot stand alone in court. The DNA profile represented a "mixed sample," and prosecution arguments relied heavily on the genetic match as proof of Vassbakk's involvement.