Prosecutors are attempting to show Peterson drove erratically and acted oddly as authorities scoured San Francisco Bay for his wife's body in early January, even suggesting he made three brief trips to a marina there because he was worried police would discover her remains.
But the defense says Peterson made the trips simply out of concern for his wife, and that his erratic driving was because he believed he was being tailed by reporters.
Modesto police Officer Mark Weiglein testified that Peterson spent more than five hours Jan. 4 at the volunteer center set up to help find his wife, Laci, and later spent time posting fliers with Laci Peterson's picture.
He also said authorities watched as Peterson and friends searched a construction yard in the town of Manteca, about 15 miles north of the Petersons' hometown of Modesto. He said officers did not know what the group was doing.
"Did anybody that you're aware of ever go and see ... that location to see if that had anything to do with a tip that came in that that's where Laci Peterson might be?" defense attorney Mark Geragos asked.
Weiglein was unaware of such a tip, and it wasn't clear from testimony whether there had been one.
Weiglein was among seven witnesses Thursday who participated in the surveillance of Peterson between Jan. 3 and Jan. 11. Each witness testified to Peterson's erratic driving during that period.
Christopher Perry, an undercover officer with the Modesto Police Department, described a day of following Peterson when he would "get on the freeway, get off at the next exit, get back on the freeway."
Geragos said Peterson believed reporters were following him.
The trial is set to resume Tuesday.
Testimony next week will focus on DNA evidence that police say places Laci Peterson on the boat that prosecutors allege Peterson kept a secret from her so that he could later use it to dispose of her body. A hair that police say is Laci's was found in a pair of pliers on the boat.
Prosecutors allege Peterson killed his wife in their Modesto home on or around Dec. 24, 2002, then drove to San Francisco Bay and dumped her body. The badly decomposed remains of Laci Peterson and the couple's fetus washed ashore in April 2003, not far from where Peterson set out for what he claims was a solo fishing trip the day Laci vanished.
Defense lawyers contend someone else abducted and killed Laci, then framed their client after learning his widely publicized alibi.