The investigator, Lydell Wall of the Stanislaus County Sheriff's Department, said a computer file he found on one of Scott Peterson's hard drives indicated Peterson had searched a fishing and boating Web site on Dec. 7, 2002.
The woman who introduced Peterson to his girlfriend testified previously that she had confronted him on Dec. 6 after learning he was married.
Prosecutors allege Peterson killed his wife in their Modesto home around Dec. 24, 2002, then drove to San Francisco Bay and dumped her weighted body from a small boat he had purchased just weeks earlier.
The badly decomposed remains of Laci Peterson and the couple's fetus washed ashore in April 2003, not far from where Peterson said he launched a solo fishing trip the day she vanished.
On Tuesday, another investigator testified that Peterson had researched water currents in the bay on Dec. 8, 2002, according to files he had examined on Peterson's computers.
Defense lawyer Mark Geragos pointed out that police also found out that Peterson had gathered information about fishing. Before his arrest, Peterson told police he was fishing alone on the bay the morning his wife vanished.
Geragos also noted that a printout of the Web site Peterson visited regarding bay currents had different times and dates on it, one showing it was checked by Peterson on Dec. 5, a day before the woman who fixed him up with Frey confronted him.
Also Tuesday, prosecutors attacked the former fertilizer salesman's character, noting he added adult programming to his satellite television service in the weeks after his pregnant wife vanished.
Donald Toy, a manager for EchoStar satellite TV service, said Laci Peterson first ordered the service at the couple's Modesto home on March 13, 2001, without an adult programming option.
But about two weeks after he reported his wife missing, Scott Peterson changed the account to include the Playboy Channel and altered the service again five days later to include more explicit adult channels, Toy said.
On cross-examination, defense lawyer Mark Geragos pointed out the adult channels Peterson selected were legal and noted that even the satellite company characterizes the programming as "adult content," not "pornography."
Before Toy took the witness stand, Geragos argued to keep his testimony from jurors, claiming it had no relevance in the case, except to "assassinate (Peterson's) character."
Prosecutors also called three witnesses who testified that Peterson seemed emotionless at a vigil for his missing wife Dec. 30, 2002.
Defense attorneys noted that none of the witnesses watched Peterson during the entire vigil, all of them were only interviewed by police this year and two were connected to Laci Peterson's mother either by friends or family members.
Another prosecution witness, Lissa McElroy, testified that Peterson seemed "fairly nonchalant" as the two looked through photo albums for pictures to help in the search for Laci within days of her disappearance.
She said he appeared to be jokingly pulling out photos of Laci in a bathing suit, another drinking with her friends and yet another of his friends with one person "mooning" the camera. She later admitted that prosecutors had her look through the photo album Monday night and she was unable to find any of the pictures she described on the witness stand Tuesday.
But prosecutors had failed to inform defense lawyers that the woman could not find any of the familiar photos, violating trial rules that prosecutors turn over exculpatory evidence.
The judge struck McElroy's testimony from the record.