Lydell Wall of the Stanislaus County Sheriff's Department, returning to the stand for cross-examination, testified that someone used Peterson's home computer to search shopping Web sites for a scarf and a sunflower umbrella stand on Dec. 24, 2002, between 8:40 a.m. and 8:45 a.m.
"Who was the person who logged on at 8:40 a.m.?" defense lawyer Mark Geragos asked.
Wall could not answer. He said authorities never asked him to determine exactly who used the home computer that morning.
Prosecutors allege Peterson killed his pregnant wife in their Modesto home either late on Dec. 23 or early on Dec. 24, then drove to San Francisco Bay and dumped her body from a boat he kept at a warehouse. The remains of Laci Peterson and the couple's unborn son washed ashore months later, not far from where Peterson said he set out on a fishing trip the day his wife vanished.
Defense lawyers contend someone else abducted and killed Laci, then framed their client after learning his widely publicized alibi.
Police allege Peterson disposed of the body on the morning of Dec. 24. With Monday's cross-examination, defense lawyers tried to show that the prosecution's timeline left little time for Peterson to get rid of the body.
Prosecutors allege Peterson made a cell phone call at 10:08 a.m. Dec. 24 at or near his home. Wall testified that Peterson was browsing Web sites at his office at 10:30 a.m. the same morning. Records indicate Peterson surfed Web sites there for 26 minutes.
Former prosecutor and trial watcher Michael Cardoza said the defense was trying to establish Laci Peterson was alive in the morning.
"That really is important to their case," Cardoza said. "It really shoots holes in the prosecution's timeline."