A detective who spent Christmas Eve questioning Scott Peterson (search) and the next four months trying to find his missing wife testified Wednesday about how officers enlisted Peterson's friends, neighbors and mistress in the effort to snare him.

Detective Al Brocchini said he called friends of Scott and Laci Peterson (search) to point out news articles about Scott's extramarital affair and a $250,000 insurance policy he took out on his wife before she vanished Dec. 24.

At one point, Brocchini made a note that he "was attempting to plant the seeds of suspicion" in a friend of Laci Peterson.

The testimony came as the defense continued cross-examining Brocchini, the first detective to investigate the disappearance of the pregnant woman. The defense has claimed investigators focused suspicion on Peterson and failed to catch the "real killers."

The officer said he tried to get friends to prod Scott Peterson for details about what happened to his wife. The remains of the 27-year-old substitute teacher and her unborn son washed ashore in San Francisco Bay (search) in April only a few miles from where Peterson said he was fishing on the day she disappeared.

Brocchini said he took part in discussions with other officers about themes that Scott Peterson's former girlfriend Amber Frey should discuss when talking with Peterson during phone calls she was secretly recording.

He said he didn't recall coaxing Frey to suggest to Peterson that there had been an accident and he panicked, but he vaguely recalled officers telling her to pretend she was a suspect in the disappearance so that Peterson would feel sorry for her and take the rap, Brocchini said.

Also Wednesday, an FBI scientist denied that a DNA sample used to link Laci Peterson to a hair on her husband's boat was contaminated.

Bruce Budowle was called by prosecutors to rebut testimony from a defense expert who had criticized the DNA techniques used to analyze the hair, found in pliers in the boat Scott Peterson said he took fishing the day his wife disappeared.

The defense witness had said that testing of mitochondrial DNA was less reliable than other DNA tests and susceptible to contamination.

Budowle said the database the FBI used to determine the probability that the hair could have been from the 27-year-old Modesto woman was large enough that scientists were confident of their findings.

The hair has become the most time-consuming element in the preliminary hearing to determine if there is enough evidence to try Peterson on charges of murdering his wife and unborn son. Wednesday was the seventh day of testimony in the hearing.

Scott Peterson's lawyer Mark Geragos renewed his request Wednesday to subpoena FBI surveillance tapes taken outside the Peterson household after Laci Peterson was reported missing.