REDWOOD CITY, Calif. — Prosecutors today kicked off closing arguments in the murder case against Scott Peterson by sharply attacking his alibi that he was saltwater fishing when his wife disappeared.

After 23 weeks, the trial of Peterson on charges he killed his wife, Laci, and the fetus she carried, moved into its combative summing up phase before going to the jury by Wednesday.

Prosecutor Rick Distaso said that Peterson's claim to be fishing alone in the area where Laci's body washed ashore in 2002 was the most important fact in the case. "Scott Peterson did not go fishing on Dec. 24, he dumped his wife's body in the San Francisco Bay.

"The only person in the exact location where Laci and Conner Peterson's bodies washed ashore is sitting right there," Distaso told jurors as he pointed at Scott Peterson, "and you can take that to the bank and convict this man of murder."

Distaso was expected to continue his closing arguments during the morning and after lunch. The defense was expected to present its final arguments Tuesday.

Peterson faces two counts of murder in the deaths of his wife and the fetus she carried. If convicted, he could face the death penalty or life without parole.

Jurors can also choose to convict on lesser charges of second-degree murder, which carries a sentence of 15 years to life in prison. Judge Alfred A. Delucchi ruled last week that he found ample evidence to support second-degree murder charges, as well as the first-degree murder counts filed against Peterson.

Prosecutors claim Peterson strangled or smothered his wife around Christmas 2002, then dumped her body into San Francisco Bay. The remains of Laci Peterson and her fetus were discovered along a rocky shoreline about four months later.

Because of the lurid details, the Peterson trial has become a staple of cable television and the tabloids. Prosecutors maintain that Peterson wanted to rid himself of a boring life with Laci and saw his mistress, Amber Frey, as a way out.

Distaso said he didn't think Peterson killed his wife to be with Frey, but "Amber Frey represented to him freedom. Freedom is what he wanted."

Frey was among the 184 witnesses who testified during the trial.

Sahagun reported from Redwood City; Times staff writer Michael Muskal handled rewrite in Los Angeles.