SANTEE, Calif. — Finally knowing who was responsible for her 29-year-old sister Diane Dahn's murder in 1988, Victoria Dahn-Minter couldn't hold back tears.
"I didn't think anything was ever going to come of this. I thought, I myself was going to go to my grave, not knowing,” Dahn-Minter said,
Thirty-four years ago, San Diego County Sheriff's deputies found Diane Dahn's nude body inside a back room of her Santee apartment with visible stab wounds to her chest but no signs of a break-in.
Her 2-year-old son Mark was found unharmed inside the apartment.
Despite DNA evidence left underneath Dahn’s fingernails, no suspects were ever identified as a match until over three decades later.
"There was a hair that was recovered at the time of her murder inside one of her hands. That hair was processed, and a full profile was obtained,” said Sheriff's Homicide Detective Brian Patterson.
Detectives used Investigative Genetic Genealogy to name suspect Warren Robertson, a tow truck driver, who lived in Dahn’s same apartment complex with his wife.
Robertson had no violent criminal history, only low-level property crimes, so investigators tracked down Robertson's relatives based on their online ancestry profiles to get a DNA sample.
"This assistance proved to be the break we needed to identify the suspect in Diane Dahn's murder,” said Senior Crime Intelligence Analyst Jeff Vandersip.
This is the fifth time the Sheriff's Homicide Unit has used Investigative Genetic Genealogy to identify a cold case suspect.
Detectives never learned a motive for Diane Dahn's stabbing. They say her killer, Warren Robertson moved to Indiana right after the murder and died in a house fire in 1999.
"This process was extremely laborious, in the end, nine trees were constructed with almost 1,300 individuals connected to the suspect,” Vandersip said.
Diane Dahn's son, Mark Beyer was adopted by Diane's friend. "I am in an interesting position because I was so young, I don't have many memories,” Beyer sad.
Beyer says he only knows that his mother was a free-spirited, accomplished musician, who loved to play the violin and worked as the first female radio repair technician at the San Diego Transit Corporation.
He is grateful cold case detectives never gave up.
"This is surreal. I was so blown away of how it transpired. It's just a huge thank you because nobody has to go back and do the things that the detectives did. The answers that my family received means closure, and closure is everything even after so much time has passed,” Beyer said.
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