Authorities say DNA solves 1988 Southern California killing; suspect died in Indiana

Authorities said Wednesday they have solved the 1988 killing of a San Diego County woman, but the suspect died in an Indiana house fire two decades ago.

Genealogical DNA testing linked the suspect to Diane Dahn, 29, who was stabbed to death in her Santee apartment, county sheriff’s investigators said at a news conference.

When she failed to show up for work on May 2, 1988, a colleague from the San Diego Transit Corp. went to her home and found her body in her bedroom. Dahn’s son, then 2 years old, was wandering in the apartment complex.

Investigators relied on testing of fingernail scrapings and a hair recovered from Dahn’s hands, authorities said.

Testing led investigators to Warren Robertson, a tow truck driver who lived in the same complex as Dahn. He died in an Indiana house fire in 1999 at age 39, authorities said.

“The investigation revealed substantial and convincing evidence that Robertson had murdered Diane,” a sheriff’s statement said.

It wasn’t clear whether the two knew each other, but both were known to be racing enthusiasts and attended stock car races at the El Cajon Speedway, the statement said.

In a video statement, Dahn’s now-grown son, Mark Beyer, said he was “blown away” by how the killing was solved.

“The answers that my family received — it’s closure and closure is everything, even after so much time had passed,” Beyer said. “And now I have a story to tell the world and tell people who cross my path.”

Dahn’s younger sister, Victoria Dahn-Minter, said she was grateful that investigators had solved the case.

“I didn’t think anything was ever going to come of this,” she said at the news conference. “I thought I myself was going to go to my grave not knowing, as well as my mother and father.”

It was the fifth cold-case killing solved through the use of genetic genealogy testing, sheriff’s officials said.

The testing matches DNA from crime scenes to commercially available DNA databases in order to track down possible relatives of suspects.

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