Within days of discovering the remains of a headless woman and a fetus along San Francisco Bay, police were so sure they had their man they moved in to arrest Scott Peterson at a San Diego golf course before DNA tests confirmed the identities, a detective testified.

It was April 18, 2003, four months after Peterson's pregnant wife vanished. Later that day, Modesto Police Detective Craig Grogan got the call that the bodies were indeed those of Laci Peterson (search) and the couple's fetus, a boy they planned to name Conner.

Grogan, seated beside Peterson in the back of a police car, said he gave the news to the man who had just been arrested for double murder.

"He and I were seated beside each other in the back of the [police] car ... He removed his sunglasses. I saw that he had lowered his head, a tear came out of his right eye, then he wiped the left side of his face," Grogan testified Thursday.

Grogan also testified that police followed several leads before arresting Peterson, including the possibility of a serial killer.

Grogan said that about week before police arrested Peterson, he searched a federal serial killer database for possible clues in Laci Peterson's disappearance.

"The information I submitted was to look to see if there were any patterns regarding pregnant females in homicide cases, serial cases involving pregnant females," Grogan said.

Grogan said Peterson's mistress, Amber Frey (search), and even Laci's family members had been considered suspects. Prosecutors allege it was Peterson's affair with Frey that drove him to kill his wife.

Defense lawyers have accused police of focusing too quickly on Peterson to the detriment of other possible leads.

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.

Her remains — and that of her fetus — washed up in April 2003, not far from where Peterson launched his boat on Christmas Eve for what he claims was a solo fishing trip.

Peterson's lawyer, Mark Geragos (search), maintains someone else abducted and killed Laci.

On cross-examination, Geragos pointed out that Peterson was cooperative and truthful with police on the first night of the investigation.

Geragos then sought to show that police honed in too quickly on his client, noting one officer told a witness on that first night that he "already knew what happened."

Geragos portrayed his client as a pacifist with no history of violence. The Petersons' friends were all "very supportive" of the former fertilizer salesman, he noted. Peterson had no prior criminal history and had never laid a hand on his wife, Grogan agreed.

"He told you that he'd never been in a physical fight or altercation in his life, is that correct?" Geragos asked.

"Yes," Grogan said.

"You ever find anybody who's ever had a fist fight or physical altercation with Scott Peterson?" Geragos prodded.

"No," Grogan replied.

Later Thursday, Geragos provided an explanation for why Peterson visited the Bay Area several times while police were searching for the bodies there: He was looking for a witness who had seen him put his boat in the water Christmas Eve. Geragos said Peterson had even hired a private investigator to help find the person.

The defense lawyer also tried to counter prosecution claims that Peterson lied to some people about his alibi. Geragos said Peterson left his wife a telephone message hours before he arrived home, telling her he was just leaving the bay marina — a point intended to show Peterson never meant to conceal anything about where he had been that day.