REDWOOD CITY, Calif. — The detective who built the double-murder case against Scott Peterson spent his seventh and final day on the witness stand Thursday arguing with a defense lawyer over whether the fertilizer salesman's behavior was truly suspicious or simply misinterpreted by overzealous authorities.

Peterson's lawyer, Mark Geragos, accused Modesto police detective Craig Grogan of putting a sinister spin on everything — whether Peterson knew his wife's voice-mail password, the amount of contact he had with police, and when he did his laundry on the day Laci Peterson disappeared.

In testifying last week about the 41 reasons he concluded the missing mother-to-be would turn up dead by her husband's hand in the San Francisco Bay, Grogan noted that he found it "odd" that Peterson had washed his clothes immediately after returning from a fishing trip.

"He's been in a boat in the bay. That seems odd?" Geragos asked dismissively.

"It does seem odd," Grogan shot back. "He comes home, finds Laci not there, that the dog has the leash attached, and that's one of the things he decided to do."

"Was there a theory that you had, that because she wanted a nicer house and because she was going to stop working, that therefore that was going to be motivation to kill her?" Geragos asked.

"I think that could add to motive," the detective said.

Grogan also acknowledged that Peterson had frequent contact with police in the wake of his wife's Dec. 24, 2002, disappearance. He testified Wednesday that Peterson did not call him on a daily or weekly basis to ask about the investigation, but, under questioning by Geragos, he conceded that Peterson talked to other officers, including a liaison officer assigned daily to the volunteer search center.

Grogan also agreed that Peterson knew he was a prime suspect in the detective's eyes.

"He's not going to be real warm and fuzzy with you," Geragos asked.

"Possibly not," Grogan said.

The lawyer also implied that Grogan was using a double standard when he called Peterson's Christmas Eve fishing trip suspicious, but did not similarly characterize a fishing trip his wife's stepfather, Ron Grantski, took the same day.

Grogan insisted the comparison wasn't appropriate and later, under questioning by prosecutor Birgit Fladager, he elaborated.

"You're looking for behaviors that are out of the normal, and it's very normal for Mr. Grantski to go fishing," Grogan said. By contrast, the detective said, Peterson usually took one fishing trip a year and "as far as I know had never fished in the San Francisco Bay before."

Evasive maneuvers

Jurors also heard Thursday from five members of a state Department of Justice surveillance team that followed Peterson before his April 18, 2004, arrest in San Diego.

According to the officers, Peterson knew he was being tailed despite their plain clothes and unmarked cars.

Agent Claude Jurban said Peterson clapped his hands in glee when he outmaneuvered a surveillance team on an interstate. Another agent, Kevin Kolbe, said Peterson walked up to his unmarked car, complimented him on a colleague's "blocking maneuver," and then asked which law enforcement agency he was from.

A supervisor of the surveillance team, agent Sonia Ramos, testified that Peterson professed ignorance about who was following him shortly after his arrest. She said that, earlier that morning, her car had "fishtailed" as she tried to keep up with a speeding Peterson on a windy road.

"He asked if I was the person that almost got in the accident," Ramos testified. She said he apologized and said "that he didn't mean to cause any harm, that he thought we were the media."

Also Thursday, hydrologist Ralph Cheng, a senior researcher at the U.S. Geological Survey and an expert about the bay's waters, began testifying. Cheng is expected to explain how the bodies of Laci Peterson and her son washed onto the shore of the bay and perhaps link their location to the area where Peterson was fishing. He spent 45 minutes walking jurors through a PowerPoint presentation on the tides and currents of the bay before Judge Alfred Delucchi dismissed the jury for the weekend.

Cheng will continue testifying Monday morning.