Scott Peterson’s lawyer continued the fight Thursday to have a small hair thrown out of the evidence against his client in the killing of his wife and unborn son during the second day of the hearing that will determine if he is tried for murder.
Defense lawyer Mark Geragos continued his attempts to sow doubt on the prosecution’s first piece of evidence, questioning an FBI expert about a type of DNA evidence that is not widely used in court, suggesting it was unreliable and based on faulty databases.
FBI lab supervisor Constance Fisher acknowledged that mitochondrial DNA, which can show links between a mother and child, is not an exact science. She said it had limitations, as did the FBI lab where tests were conducted.
Fisher said that a computer program used in the analysis had several glitches and that lab equipment routinely broke down. But she said those problems didn’t impair the results that showed a link between a hair found in a pair of pliers in Scott Peterson’s boat with a DNA swab from the mouth of Laci Peterson’s mother.
The analysis cannot show an identity match with the same level or reliability as so-called genetic fingerprinting DNA techniques usually introduced in court.
Although the defense will present its own expert to rebut the testimony and question the DNA analysis next week, the hearing Friday will turn to testimony from the last people to see Laci Peterson alive.
The couple’s housekeeper is expected to take the stand to provide insight into the condition of their home and Laci Peterson’s disposition in her final days. Prosecutors also plan to call Laci Peterson’s family members to testify.
The hearing, which is expected to last through next week, will determine whether Peterson, 31, is tried for murder in the deaths of his pregnant wife and the baby boy she was carrying.
Scott Peterson, a fertilizer salesman, said he last saw his wife the morning of Christmas Eve when he left the house to go fishing.
The remains of the substitute teacher and the fetus were discovered nearly four months later on the shores of San Francisco Bay near where he said he was fishing.
Although the hair found in the boat does not provide an exact match with Laci Peterson, it can’t be ruled out as her hair and could be used to support a possible prosecution theory that Peterson ferried his wife’s body to a watery grave.
Geragos is challenging the admissibility of the testimony, saying the analysis was the subject of a raging debate in the scientific community and suggesting the hair sample may have been contaminated or tampered with by law enforcement.
Fisher minimized the debate and said the science had been used by anthropologists for decades and by the FBI since 1996.
The technique has not been widely accepted in courts, and it was only ruled admissible once in a California state court, in the case of an accused murderer in San Diego.
Geragos asked Fisher why the FBI didn’t try to match the hair from the boat with a bone from Laci Peterson’s remains.
She said that test would have produced the same results as an analysis comparing the hair with the sample taken from her mother.
The grilling became tense at moments as Geragos hovered over the witness stand, dissecting minutiae from Fisher’s findings.
But the tension snapped during a light moment as Geragos asked why the FBI employee who developed the faulty computer program used in the analysis was no longer employed by the federal agency.
“Did he get fired for incompetence?” Geragos asked.
He went to law school, Fisher said, causing a roar of laughter in the courtroom. Scott Peterson joined in.