"(He) wasn't talking about Laci. He was talking about where he was in Europe," police detective Al Brocchini said under cross-examination when questioned about Peterson's ex-mistress, Amber Frey, who is due to testify later in the hearing.

Peterson had not actually been in Europe at the time and Brocchini's account of his conversation with Frey suggests he was trying to establish an alibi by placing himself away from the scene of the crime.

An eight-months pregnant Laci Peterson disappeared from her Modesto, California, home last year on Christmas Eve. Months later her body and that of her unborn son washed out of the bay near San Francisco.

By the time Peterson talked with Frey about traveling to Europe, she was already cooperating with investigators and allowing them to secretly tape their conversations, Brocchini said.

Also on Wednesday, a senior FBI scientist said that a special type of DNA testing used to identify a hair from Laci Peterson's head was reliable and had even been used in discovering the names of Sept. 11 victims.

Bruce Budowle, a senior FBI scientist, was called by prosecutors to rebut testimony by the defense's DNA expert, William Shields, who said last week that the FBI's testing procedures are susceptible to contamination and misinterpretation.

Defense attorneys are trying to persuade Stanislaus County Superior Court Judge Al Girolami to disregard the hair evidence found on a pair of pliers on Peterson's boat on grounds that the reliability of the FBI's mitochondrial DNA testing is a subject of scientific debate.