Redwood City, Calif. ? The judge in Scott Peterson’s murder trial postponed cross-examination of a key prosecution witness Wednesday, citing a “potential development” that needed to be “checked out.”

Defense attorney Mark Geragos had planned to question Peterson’s former girlfriend, who testified last week that the fertilizer salesman began a relationship with her just weeks before his pregnant wife disappeared.

Superior Court Judge Alfred A. Delucchi gave no further details, and the lawyers are under a gag order that bars them from talking to the media. After a closed-door meeting with attorneys, Delucchi sent jurors home for the day around 10 a.m.

Trent Copeland, a defense attorney who has been tracking the case, said he did not believe it was a “bombshell piece of evidence” but said he was convinced that it had to do with the testimony of Amber Frey, the defendant’s former girlfriend. Others speculated that a new tip or potential witness could be involved.

Frey’s attorney, Gloria Allred, said the delay came as a surprise.

“It is, of course, frustrating to Amber, because she was ready,” Allred said.

Frey, a massage therapist from Fresno, recorded hundreds of phone calls with Peterson from December 2002 until February 2003. Prosecutors played two dozen of those conversations for jurors. The testimony is intended to show that Peterson killed his wife, Laci, in part to be with his new girlfriend.

Frey is now scheduled to testify Monday morning.