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Suspect Identified 34 Years After California Mother Found Stabbed To Death In Her Bedroom

Authorities say Warren Robertson lived as a tow truck driver in the same apartment complex where Diane Dahn was murdered in 1988.

Warren Robertson Diane Dahn Pd

Officials in San Diego say they’ve finally identified the man responsible for murdering a mother in her apartment 34 years ago. 

Diane Lynn Dahn, 29, was found dead on May 2, 1988, when a coworker visited her Santee, California, residence after she failed to show up for work, according to the San Diego County Sheriff’s Department. With the help of genetic genealogy, authorities say they’ve identified a tow truck driver named Warren Robertson as the man who beat and stabbed Dahn to death in her bed more than three decades ago.

“It doesn’t make the pain go away,” said Dahn’s sister, Victoria Dahn-Minter. “But at least there’s an answer.”

Dahn — a communications technician — was nude in her bed when she was discovered, a spokesperson for the sheriff’s department told the LA Times in 1988. A medical examiner determined someone bludgeoned Dahn and stabbed her in the chest.

Dahn’s 2-year-old son was found wandering around the Graves Avenue apartment complex as his mother lay dead inside, according to the sheriff’s department. Years later, he would have no recollection of the incident. 

Despite an extensive investigation, the case remained unsolved. Over the years, investigators made several attempts to find Dahn’s killer, but to no avail. 

In 2000, DNA was collected from underneath the victim’s fingernails and later identified as the suspect’s, but the profile did not reveal a specific individual, authorities stated. The following year, attempts to run the sample through the FBI’s Combined DNA Index System (CODIS) were unsuccessful when the DNA was found to be “insufficient.”

In 2010, authorities collected another DNA sample from a hair found in Dahn’s hand, matching the previous sample taken from her fingernails. However, another submission to CODIS yielded no results. 

Apartment Diane Dahn Pd

It wasn’t until 2020 when the sheriff’s cold case team joined forces with the crime lab and utilized genetic genealogy, the now-common practice of identifying an individual through genealogical markers matching a biological relative. Authorities withheld the genetic relationships of those identified as the suspect's relatives but traced them through nine family trees.

In this case, authorities confirmed the unknown male’s DNA belonged to Warren Robertson, who was “determined to be the donor of previously known DNA.”

Authorities said Robertson, who would have been 27 or 28 at the time of Dahn’s murder, lived at the same apartment complex as the victim in 1988. A thorough investigation revealed Robertson was born in Arkansas but spent most of his younger life “in the San Diego region.” He was a local tow truck driver who left his family shortly after the murder to live in Lakeside before eventually moving to Indiana in 1989. 

On Nov. 25, 1999, Robertson died in a house fire, according to the sheriff’s department. Investigators were unable to determine whether Robertson and Dahn knew each other but claimed they were both race car enthusiasts who went to the El Cajon Speedway in the year of Dahn’s murder. 

“The San Diego County Sheriff’s Department is committed to bringing answers to families no matter how long ago the crime occurred,” said acting Sheriff Kelly Martinez. “I hope this brings some sense of peace and healing to the victim and her family.”

Family members also spoke out about the identification of Robertson, including Mark Beyer, the 2-year-old found wandering around the apartment complex after his mother’s brutal murder.

Mark Beyer Pd

“Looking back, some of the struggles you go through, if you feel alone because of what you went through, you lost your mother,” said Dahn’s son. “You know you have family, you know you have family who loves you, but sometimes, you do feel alone all the time. Just good work for the homicide unit that I was so blown away when I heard the story of how it actually transpired. Like, how you go from what little information you have to building a case like that was truly impressive.”

Victoria Dahn-Minter, also praised the authorities’ dedication to her sister’s case while lamenting that her nephew grew up without a mother, according to the sheriff’s department. 

“Thirty-four years is a long time to be in a state of grief and immense sorrow. Not knowing almost consumed me,” said Dahn-Minter. “My sister was an amazing person. She loved life and always played the violin and guitar. It’s unfortunate my nephew never had the chance to know his mom. She was a great mother. The detectives did such a wonderful job. They were persistent. Whenever I would call to follow up, they knew Diane’s name and her case right away. I didn’t think anything was ever going to happen.”

Diane Dahn’s son said the identification of Warren Robertson comes just two weeks after what would have been his mother’s 63rd birthday. 

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