San Mateo County to reexamine old murder cases using new DNA tools
The San Mateo County Sheriff’s Office recently was awarded a $217,178 federal grant to use DNA analysis to help solve “cold” homicide and sexual assault cases.
The U.S. Justice Department grant will allow the county’s forensic scientists to upgrade their equipment and add staff to re-examine 247 unsolved cases, the oldest dating to 1970. In each of those cases, a suspect left some sort of genetic clue — a saliva bite, semen, skin cells, a strand of hair or a piece of clothing left at the crime scene – but the technology at the time was not advanced enough to yield a DNA sample.
With the grant money, the Sheriff’s Office can upgrade equipment to allow biological evidence from the cold cases to be run against a database filled with genetic profiles of known criminals. “The primary mission is to solve crimes and this is a tool to do that,” said Alex Karagianes, director of the sheriff’s forensic lab.
The county database is organized by 15 genetic markers. After a suspect was convicted, authorities took samples of his or her DNA and generated a profile to go into the database. If the potential offender does not appear in the database, the system will search for profiles from crimes in other jurisdictions, seeking a possible match.
In 2004, California voters approved Proposition 69, which gave law enforcement the ability to collect fingerprint and DNA samples from a suspect at the time of arrest rather than waiting for a conviction. Since 2009, when the database started to include samples taken after any arrest, San Mateo County has seen a 40 percent increase in database matches, Karagianes said.
This larger pool of DNA samples increases the likelihood of identifying a potential offender from any of the unsolved cold cases — once the Sheriff’s Office gets more advanced technology as a result of the grant money, which could take up to five months.