A homeless man sneaked past guards at a gated Malibu community to get to Mel Gibson's home because he believed God had sent him to pray with the maker of "The Passion of the Christ," a prosecutor has told a court.

Deputy District Attorney Debra Archuleta said on Wednesday Zack Sinclair, a 34 year-old from Idaho, began writing letters to Gibson last July claiming he was on a mission from God.

"Mr. Sinclair believes he is being told by God to pray with Mr Gibson," she told the jury at the opening of Sinclair's trial in which Gibson is due to testify on Thursday.

Sinclair, who prosecutors say has a history of mental illness and a prior case of stalking in Idaho, is charged with one count of felony stalking.

Gibson wrote, directed and produced the blockbuster movie "The Passion of the Christ" about the last hours in the life of Jesus, which came out last spring.

Sinclair, acting as his own lawyer, said in a brief opening statement he would not question witnesses because the burden of proof was going to be "too heavy" for prosecutors.

Gibson's security chief, Jerry McKay, testified that Sinclair sent Gibson 12 letters in which he said God had sent him to California to pray with the movie star. Sinclair wrote that he had spent over two years in jail in Idaho for stalking a mentally ill woman, McKay said.

Los Angeles County Sheriff's Deputy Mark Winn told jurors Sinclair had walked up a creek bed to avoid security guards to get to the actor's home.

Winn, who confronted Sinclair outside Gibson's home, said when he told him he had to leave and could not return, Sinclair became "teary-eyed."

"He was kind of in disbelief that he was not allowed to go on with his mission," Winn said.

Throughout the testimony Sinclair, dressed in a Navy blue blazer with a checked tie, sat passively and made only a few notes.