Mysterious 20-Year Death Identified Using Genetic Genealogy Techniques

Phoenix, Arizona — A man whose identity remained unknown for over two decades has been identified as John Thiellesen, thanks to advanced genetic genealogy techniques. Thiellesen was found unconscious on the sidewalk at Third Avenue and West Madison Street in August 2004 and later died in a hospital from heat exposure.

At the time, emergency responders and police could not determine his name, and no relatives came forward. He was described as 6 feet 2 inches tall with scars on his abdomen and forearms, estimated to be between 30 and 55 years old. The Phoenix Police Department attempted to identify him through fingerprints and DNA samples but had no success for years.

The breakthrough came after the Maricopa County medical examiner referred the case to the Investigative Genetic Genealogy Center at Ramapo College in New Jersey in September 2024. A blood sample was sent to genomic researchers at Genologue in Georgia, and subsequently analyzed at Parabon Nanolabs in Virginia.

On the last day of the semester, researchers found living relatives of Thiellesen. Christen Eggers, a senior medicolegal death investigator, confirmed the identity after consulting with the Arizona Attorney General’s Cold Case Unit.

In a statement, Eggers expressed gratitude for the college’s role, saying, “Ramapo College has become a beacon of hope for individuals and families across the nation.” Cairenn Binder, assistant director of the IGG Center, highlighted the importance of their work, calling it a demonstration of the power of investigative genetic genealogy.

Thiellesen had been reported missing in Toledo, Ohio, by his brother, who indicated that he suffered from mental health issues. It remains unclear how he ended up in Arizona. The identification has brought closure to a case that had puzzled law enforcement and the community for many years.

As technology advances, the hope remains for families with missing loved ones that cases like Thiellesen’s can be solved.