Scott Peterson (search) offered his own theory of what happened to his pregnant wife within 24 hours of her disappearance, the lead detective testified Monday at Peterson's double-murder trial.

Modesto police Detective Craig Grogan said the comments were among several things Peterson said and did in the early days of the investigation that made him suspicious.

Peterson theorized that Laci Peterson (search) "had been wearing jewelry that she inherited from her grandmother and that he'd seen her wearing it on that morning, and when she went into the park a transient had robbed her," Grogan testified.

Grogan later said police found in the house all the jewelry Peterson said his wife had been wearing that morning, except for a pair of diamond earrings.

Grogan conducted a three-hour, unrecorded interview of Peterson on Dec. 25, 2003, a day after Laci Peterson was reported missing.

Prosecutors allege Peterson killed his eight-months-pregnant wife on or around Dec. 24, 2002, in their Modesto home, then dumped her weighted body into San Francisco Bay (search).

The remains of Laci Peterson and her fetus washed up along a bay shore in April 2003, not far from where Scott Peterson launched his boat that Christmas Eve morning for what he claims was a solo fishing trip.

Defense lawyers maintain that someone else killed Laci after abducting her as she walked the couple's dog.

Grogan in other testimony shed light on why police focused on Peterson early in the investigation.

The detective said Peterson's alibi couldn't be immediately corroborated, and that he was the last person to have seen Laci.

Grogan said it also was suspicious that Scott Peterson washed his clothes immediately after returning home that morning. "That led us to believe that possibly a cleanup had occurred at the house," he said.

Previous witnesses have testified that none of Laci Peterson's blood was found in the home.

Grogan said it was Scott Peterson's story and "unusual" behavior that led police to seek search warrants for his home and warehouse, where he stored the boat prosecutors allege he used to dispose of his wife's body.

Grogan said he grew even more suspicious of Peterson when he searched the warehouse and discovered concrete residue on a boat trailer and five circular-like voids in the cement dust.

Peterson told police he made a cement anchor at the warehouse for his boat. Prosecutors claim Peterson made five cement anchors, only one of which was found on his boat. They allege he used the other four anchors to sink his wife's body.

"It looked like a tremendous mess for making one eight-pound anchor," Grogan said.

Grogan said that in a Jan. 2 conversation, Peterson again said something that struck him.

"He brought up the idea ... Laci had been abducted so that the child could be taken from her," Grogan said. "He said, 'Do you think when she has the baby that I'll get half my family back?"'

Grogan detailed the investigation for jurors, explaining how he even questioned Laci's half-sister and brother to rule them out as suspects.

Laci had recently inherited about $100,000 worth of jewelry from her grandmother and stood to gain an additional $160,000 from the estate, according to previous testimony.

Grogan said he interviewed her relatives to see if anyone "had a financial motive to dispose of Laci." He later confirmed their alibis for the day Laci vanished.

Monday brought a shift in the prosecution's strategy with the questioning of Grogan being done by Stanislaus County Chief Deputy District Attorney Birgit Fladager. The case's lead prosecutor, Rick Distaso, sat in the front row of the gallery.

The reason for the change or how long it would last were unclear. Attorneys are bound by a gag order.

Grogan was expected to continue testifying into next week, Judge Alfred A. Delucchi told jurors. Delucchi said the prosecution should wrap up its case by Sept. 30, 18 weeks after it began.

Earlier Monday, Scott Peterson's lawyers continued their attempts to show that police ignored important leads that could have pointed suspicion elsewhere.

Detective Ian Frazer, of the East Bay Regional Park District police, testified about the discovery of Laci Peterson's remains along a rocky shoreline. On cross-examination, the questioning turned quickly to a large plastic bag found near Laci's remains.

Defense lawyers have suggested the plastic may have had something to do with Laci's death, although an earlier prosecution witness testified there was no blood or tissue found on the plastic.

Defense attorney Mark Geragos noted that Frazer stated previously, outside court, that he and another officer detected a "decomposition" smell on the plastic.

Geragos noted the detective was scheduled to testify last month, but the revelation about the smell, provided to defense attorneys before Frazer's testimony was to begin, led to a several-day delay. The delay was due, Geragos said outside court at the time, to "potentially exculpatory" evidence.

Frazer testified he told Modesto detectives about the smell before the trial, but Geragos noted that no mention of the smell was found in any Modesto police reports.

"Obviously somebody thought [the plastic] was significant, right?" Geragos asked.

"That is correct," Frazer said. "I believed there might be a connection."