A judge in Scott Peterson's (searchmurder trial Thursday sealed an anonymous letter while defense attorneys investigate its claims someone else may have killed the defendant's pregnant wife.

Since authorities arrested Peterson a year ago for the December 2002 slaying of Laci Peterson and her unborn child, defense lawyers have offered their own theories of what happened — including that members of a satanic cult abducted her.

"We received a letter from an anonymous citizen indicating who they feel is responsible for the killing in this case," Judge Alfred A. Delucchi (searchsaid during a break in jury selection.

Defense attorney Mark Geragos (searchsaid his office would investigate the claims. Citing a gag order in the case, he refused further comment.

It was not the first time the case touched on what defense lawyers assert could be an exculpatory lead.

Prosecutors last week said they'd conduct DNA tests on blood found inside a van that witnesses reportedly saw in the neighborhood around the time Laci Peterson vanished. Prosecutors said they remain convinced the vehicle was not involved, but are conducting the tests in anticipation of the defense's strategy. Geragos has hinted the van and its occupants may have been linked to Laci Peterson's disappearance.

Jury selection is set to continue Monday. Opening statements are scheduled for May 17.

Scott Peterson could face the death penalty or life without parole if he is convicted on the two murder charges.