Prosecutors may use mitochondrial DNA extracted from hair found in Scott Peterson's boat in their attempt to prove he killed his pregnant wife and dumped her body in San Francisco Bay, a judge ruled Monday.
Mitochondrial DNA has rarely been used as evidence in California court cases and it can't provide a definitive match. The defense challenged the evidence as unreliable.
But Stanislaus County Superior Court Judge Al Girolami said prosecutors could tell a jury that chances are the mitochondrial DNA from that specific strand of hair could be found in one out of every 112 Caucasians.
The ruling came in the fourth week of the preliminary hearing to determine whether there's enough evidence against Peterson to warrant a murder trial.
Peterson, 31, has pleaded not guilty to killing his wife, Laci, and unborn son and could face the death penalty if convicted.
Peterson left the courtroom Monday when testimony turned to the state of his wife's corpse and the remains of their son.
Forensic pathologist Dr. Brian Peterson, no relation to the couple, said he could find no evidence of wounds and could not determine what weapon may have been used. He attributed the bad state of her body to prolonged submersion in the bay.
Investigators believe a human hair found in pliers in Peterson's boat came from his wife, who disappeared from their Modesto home around Dec. 24, 2002. Her body and that of the couple's unborn son washed ashore in April near Richmond, Calif.
FBI experts extracted mitochondrial DNA from the hair, and a state criminalist testified Friday that it resembles strands from Laci Peterson's brush.