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Man suspected in San Diego 1988 cold case killing identified as tow truck driver who died in fire

"Thirty-four years is a long time to be in a state of grief and immense sorrow,” a relative said. “Not knowing almost consumed me.”

The suspect in a long-unsolved San Diego murder was identified Thursday as a tow truck driver who died in a house fire more than two decades ago, authorities said. 

The San Diego County Sheriff’s Department said Warren Robertson was responsible for the murder of Diane Lynn Dahn, whose body was found May 2, 1988, in the bedroom of her San Diego apartment. 

Dahn, 29, was found bludgeoned and stabbed to death after she failed to show up for work at the San Diego Transit Corp., the sheriff’s department said in a release. 

Diane Dahn.
Diane Dahn.San Diego County Sheriff's Department

Her 2-year-old son was found wandering around the family’s apartment complex.

The sheriff’s department attributed the identification to a combination of DNA testing and genetic genealogy. 

Beginning in 2020, investigators developed a DNA profile from crime scene evidence — a strand of hair found in Dahn’s hand — and uploaded it to commercial genealogy sites. Authorities described the process as so exhaustive that it produced nine family trees.

Direct relatives of Robertson eventually provided DNA samples, confirming that it was his hair in Dahn's hand.

Investigators discovered that Robertson spent most of his early years in San Diego and lived in the same apartment complex as Dahn.

Warren Robertson.
Warren Robertson.San Diego County Sheriff's Department

They both attended stock car events at a local racetrack, but it wasn’t clear whether they knew each other, the sheriff’s department said.

A year after Dahn's killing, Robertson left his family and moved to Indiana, the sheriff's department said. He died in a house fire Nov. 25, 1999. He was 39.

In a statement, Dahn's younger sister, Victoria Dahn-Minter, recalled her sibling as an amazing person, a great mother and a musician who played the guitar and the violin.

"Thirty-four years is a long time to be in a state of grief and immense sorrow," she said. "Not knowing almost consumed me."

She added: "I didn’t think anything was ever going to happen. It doesn’t make the pain go away, but at least there’s an answer.”