Faced with a barrage of pointed questions about his investigation, Detective Allen Brocchini (search) has often appeared off-guard, answering many with the response, "Can I look in my report."

Near the end of his fourth day on the witness stand, Brocchini watched the clock hanging on a wall above the jury.

Defense attorneys in Scott Peterson's (search) double-murder trial have attacked his investigation as shoddily executed and designed from the start to implicate Peterson.

Brocchini, the first investigator assigned to the report that Laci Peterson (search) had vanished, was due back on the stand Tuesday for another blistering round of questions from defense lawyer Mark Geragos (search), who has used several prosecution witnesses to attempt to explain how Laci Peterson's disappearance and murder could have come at the hands of someone other than her husband.

In his rambling cross-examination Monday, Geragos asked Brocchini about several tips police received early in the investigation, including one on Dec. 26, 2002 — two days after Laci was reported missing — that she was being held in a storage bin about 30 miles from her hometown of Modesto.

Brocchini said he knew of it, but did not have much information.

Geragos said police flew over the area with a helicopter equipped with a heat-seeking device and discovered what could have been a sign of life, but officers never searched the area.

Peterson, 31, is accused of murdering his pregnant wife on or around Dec. 24, 2002, then sinking her body in San Francisco Bay. Defense lawyers say he was fishing on the bay when Laci Peterson disappeared, and that someone else abducted her near their Modesto home as she walked the dog, and held her captive before killing her and dumping her body in the bay to frame Peterson.

Geragos then asked the detective about a report from police in nearby Tracy that a man of Pacific Island descent had tried to kidnap a 15-year-old girl a few days before Laci's disappearance.

Witnesses have said they saw a van with three "dark-skinned" men in the Petersons' neighborhood around the time Laci vanished. It's a detail Geragos has continually brought up in the trial as he works to create reasonable doubt and tries to show police ignored any leads that didn't point to Peterson.

Brocchini said he never followed up on that tip, despite the man's description as dark-skinned.

Then there was the burglary of the Petersons' home on Jan. 19.

Brocchini testified that a woman admitted robbing the Petersons' home and said she was infatuated with Scott Peterson. Geragos pointed out several lies the woman told Brocchini, including details about items she stole from the house and how she said she was working on Dec. 24 when, in fact, she wasn't.

"At that point did you become suspicious of her?" Geragos asked.

"No," Brocchini said.

But the detective acknowledged asking the woman her whereabouts on Dec. 23 and Dec. 24, as if indicating he had at least some suspicions she may have been involved in Laci's disappearance.

The woman told Brocchini she had been visiting with her ex-boyfriend and some of his friends, men of Hawaiian descent; Geragos again alluded to suspicious "dark-skinned" men seen in the Petersons' neighborhood.

Geragos then moved on to questioning about Peterson's mistress, Amber Frey (search), who first phoned police on Dec. 30 about her affair with Peterson — a day after a $500,000 reward was posted in the case. Geragos hinted she might have hoped to profit.

Brocchini also acknowledged that police investigated Frey.

Trial watchers say Geragos is working to create other reasonable explanations for Laci Peterson's murder and trying to undo the prosecution's case.

"Now, he's got this woman who was obsessed with Peterson ... maybe it could cast a little doubt," said Robert Talbot, a professor at the University of San Francisco School of Law. "But his strategy also forces the prosecution to deal with all these other avenues and breaks up their case."

Dean Johnson, a former San Mateo County prosecutor and now a criminal defense attorney who has watched most of the trial from inside the courtroom, said Geragos' style is stealing momentum from the prosecution.

"Their own case is getting buried," Johnson said.