Warren Robertson

On March 15, 2022, the San Diego County Sheriff’s Department announced that Warren Robertson is the lead suspect in the May 2, 1988 murder of 29-year-old Diane Lynn Dahn in Santee, California. The case has been cleared by exception due to the death of Robertson.

A co-worker came to Dahn’s apartment that afternoon when she failed to show up for her job at the San Diego Transit Corporation. Her 2-year-old son, Mark Beyer, was found wandering around the apartment complex. She had been bludgeoned and stabbed to death in her bedroom.

A partial DNA profile was developed in 2000 from tissue collected from under Dahn’s fingernails. The profile was not of a high enough quality to be submitted to CODIS. In June of 2010 a new DNA profile was developed from a human hair found in Dahn’s hand at the time of her death. That profile was entered into CODIS but received no hits. The FGG investigation was reportedly conducted by the San Diego County Sheriff’s Office Cold Case Team. As many as 9 family trees composed of nearly 1300 individuals were constructed in order to identify Robertson. The final confirmation was made to living relatives.

Robertson lived in the same apartment complex as Dahn at the time of their homicide, and it is not known whether they knew each other. He and his family moved to Lakeside, California shortly after Dahn’s murder, and later to Indiana. He died in a house fire in November of 1999 at the age of 39.


Ebrahimji, Alisha. “Her Murder Stumped Investigators for 34 Years. Now, DNA Evidence Points to a Neighbor as Her Killer, Police Say.” CNN, March 18, 2022. Accessed March 18, 2022. https://www.cnn.com/2022/03/18/us/san-diego-cold-case-solved/index.html.

San Diego County Sheriff’s Department. “Genetic Genealogy IDs Suspect in 1988 Neighbor Killing.” Forensic Magazine, March 18, 2022. Accessed March 18, 2022. https://www.forensicmag.com/584349-Genetic-Genealogy-IDs-Suspect-in-1988-Neighbor-Killing/.

San Diego County Sheriff’s Department. “Media Advisory: Cold Case Solved.” San Diego County Sheriff’s Department (Press Release), March 15, 2022. Accessed March 18, 2022. https://www.sdsheriff.gov/Home/Components/News/News/1019/?utm_medium=email&utm_source=govdelivery&fbclid=IwAR2gYxdVGEpZQTa_DR9FUvQOOWnxBkyu5xH1StKUAsM_MYIdXPfmr2imJZg.


First Name Warren
Last Name Robertson
Other Names
Victims 1 (Details)
IGG Started 2020-05-00
Case Cleared 2022-03-15
IGG Org San Diego CSD CCT


Case ID Name Age Case Opened Location Investigating Org Most Serious Charge Disposition Court
1665 Diane Dahn 29 1988-05-02 Santee, CA San Diego CSD Second degree murder Case was cleared by exception due to death of perpetrator n/a

Last updated: February 9, 2024

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Case data and narrative licensed under CC BY 4.0: Dowdeswell, Tracey (2023), “Forensic Genetic Genealogy Project v. 2022”, Mendeley Data, V1, doi: 10.17632/jcycgvhm96.1. All other content, including photos, have been added.