A police officer described Thursday how authorities cast a wide net in the days after Laci Peterson (search) vanished, following tips that she had been seen in a nearby park and another that she was being held captive about 30 miles from her Modesto home.

Prosecutors in Scott Peterson's (search) double-murder trial appeared to use Modesto police Sgt. Timothy Helton, at least in part, to establish that police followed other leads and didn't, as defense attorneys claim, focus solely on Peterson, ignoring other suspects.

Helton testified about several occasions where officers tracked down leads, including one from the California Highway Patrol that Laci was possibly being held and abused in a home near Tracy, about 30 miles from Modesto.

Police "searched five residences and they developed no leads," Helton said.

Prosecutors allege Peterson, 31, murdered his pregnant wife in their Modesto home on or around Dec. 24, 2002, then dumped her body from his small boat into San Francisco Bay. Peterson has told police he went fishing on the bay that Christmas Eve morning and returned to an empty house.

When the remains of Laci Peterson and her fetus washed ashore nearly four months later, near where Peterson claimed to have been on his solo fishing trip, he was arrested

Peterson could face the death penalty or life without parole, if convicted.

Under cross examination Thursday, defense attorney Mark Geragos (search) asked Helton if police thoroughly investigated the tip about Laci being held in a home near Tracy.

Helton said helicopters with heat-seeking devices flew over the area searching for signs of life, but he acknowledged that authorities never searched the buildings on the property.

Geragos claims someone abducted Laci Peterson and dumped her body in the bay to frame his client after Peterson's alibi was widely publicized.

On Wednesday, Modesto police Sgt. Ron Cloward testified that he was put in charge of the search efforts on Dec. 26, two days after Scott Peterson said he last saw his pregnant wife.

Searchers first scoured a park near the couple's home and checked with registered sex offenders in the area, Cloward testified.

The search then expanded to cover the entire city of Modesto, in manholes, rivers, alleys, canals and orchards, Cloward said.

Officers also questioned Peterson about his fishing trip and said they became immediately suspicious when he couldn't say what he'd been angling for.

Within three days of her disappearance, the search moved to the marina in Berkeley, where Peterson told authorities he had launched his boat, Cloward said.

He said the first search of the marina came Dec. 28 and was followed by 26 subsequent searches of the water until the day Laci Peterson's fetus, a boy the couple planned to name Conner, washed ashore April 13. Laci's body washed up a day later. Twenty-three more searches of the area followed, Cloward said.

On cross-examination, Geragos raised the idea that transients who frequented a park near the Petersons' home could be responsible for Laci Peterson's demise, and floated the possibility that a van seen in the area could be connected.

Scott Peterson told police his wife was preparing to walk the couple's dog, McKenzie, in the nearby park on the morning she vanished.

"There were witnesses who reported seeing the dog running around in the park loose on the leash, isn't that correct?" Geragos asked. "And the dog with the leash on is pacing back and forth and barking like crazy?"

Cloward said he was unaware of the tip.

"With that information you also had various witnesses who said they were either jogging down in the park or walking down in the park and had seen a pregnant woman who appeared to be Laci?" Geragos asked.

"Yes," Cloward replied.

Geragos shifted to the van theory.

"A number of witnesses have indicated that they had seen a van with suspicious people in the neighborhood on the morning of the 24th?" Geragos asked.

"Correct," Cloward said.

"You believed that could have something to do with Laci Peterson's disappearance, right?" Geragos prodded.

"There was a possibility that it could," Cloward replied, acknowledging that police searched for the van but never located it.

Geragos then seized on authorities' efforts to track down registered sex offenders in the area -- 74 of them, he noted, adding that five were in jail and many could not be found.

Geragos also said 47 of the sex offenders listed their addresses as a homeless mission not far from the Petersons' house.

A Peterson neighbor previously testified that transients often walked through the neighborhood between the shelter and the park, where many of them spent the day.