An investigator who recorded numerous phone calls showing Scott Peterson (search) may have repeatedly lied about his whereabouts in the weeks after his pregnant wife vanished acknowledged Thursday that the wiretaps did not capture all of Peterson's calls.

Steven Jacobson, an investigator with the Stanislaus County District Attorney's Office, spent most of Wednesday testifying about tapes of Peterson's telephone calls recorded in the weeks after Laci Peterson (search) disappeared on December 24, 2002. According to police, Peterson often lied to friends and family members about his whereabouts — telling his mother he was in Fresno, for example, when cell phone records indicate he was actually 185 miles away in Berkeley — and that he pretended to be more involved in the search for his missing wife than he really was.

On Thursday, defense attorneys sought to discredit a series of phone calls suggesting Peterson lied to his mother about following up on a tip that Laci might have been spotted in Washington state.

In a phone call January 30, Peterson could be heard talking to a reporter about a possible sighting of his missing wife in Longview, Wash. The following day, Peterson is heard telling his mother that he had discussed the tip with authorities in Longview when in reality he hadn't spoken to anyone there, according to Jacobson.

"Did Mr. Peterson make any call to the Longview Police Department (search)?" Prosecutor Rick Distaso asked Wednesday.

"No sir," Jacobson said.

But under cross examination Thursday, Jacobson acknowledged that Peterson had called the Longview police on January 30, but that the call hadn't been properly recorded.

"You did not get audio on that?" Geragos asked, referring to the wiretaps.

"That's correct," Jacobson said. "Not every one of those calls has audio."

Jacobson also testified that on February 3, when Peterson learned from a detective in Longview that the tip was bogus and that he should call the Modesto Police Department (search) for more information, Peterson had immediately done so.

Geragos also noted that authorities could not rule out the possibility that Peterson called Washington police from telephones not being monitored with wiretaps.

On Wednesday, Jacobson testified that he once suspected coconspirators and even the former fertilizer salesman's mistress in the disappearance of Peterson's wife — a turn in the 13-week old trial that may foreshadow a portion of the defense case that Peterson had nothing to do with the murder of his pregnant wife.

Geragos pointedly asked Jacobson about details he included in affidavits written to secure warrants for the wiretaps.

"One of the reasons you wanted to get a wiretap is because you believed there were coconspirators in this case?" Geragos asked.

"Yes sir," Jacobson replied.

"Because you believed that the abduction of Laci Peterson could not" have been done by one person? Geragos prodded.

"I believed that there could possibly have been more than one person involved in Laci's disappearance," Jacobson replied.

Jacobson even wrote in one of the affidavits that "there was no way one person could have done that to Laci Peterson."

On Wednesday, Jacobson also acknowledged that police at one time suspected that Peterson's mistress, Amber Frey (search) may even have been involved.

She is no longer considered a possible suspect.

"Law enforcement was mistaken," Jacobson testified. "We were operating under not a valid concern there."

Prosecutors allege Peterson killed his wife in their Modesto home on or around Dec. 24, 2002, then dumped her weighted body from a small boat into San Francisco Bay. The badly decomposed remains of Laci Peterson and the couple's fetus washed up along a bay shore in April 2003, not far from where Peterson said he launched a solo fishing trip the day he reported her missing.

His defense attorneys claim he was framed after the real killer learned of his widely publicized alibi.