LONG BEACH, Calif. (AP) _ A judge will allow attorneys to offer a post-traumatic stress defense in opening statements at the trial of a man who claims a World War II flashback made him hunt down and kill his son-in-law.

The ruling came during a pretrial hearing Tuesday for 77-year-old Richard Keech, who is charged with first-degree murder for shooting Nicholas Candy in May 1996. Keech claims he went for his gun after thinking he was back in Japanese POW camps in the Philippines more than 50 years ago.

Superior Court Judge William Garner said he won't decide whether post-traumatic stress disorder can be used as a defense until after Keech testifies _ and Garner determines whether lawyers have established a foundation for arguing post-traumatic stress disorder.

Candy, 47, and his estranged wife, Nancy, 38, were in the middle of a bitter divorce and custody battle.

Candy arrived at Keech's Long Beach home to pick up his son, Martin, then 14 months old, and was shot once. Keech then chased Candy down the street and finished him off with four bullets in the back as he lay face-down on a neighbor's lawn.

Neighbors saw it happen, and Keech doesn't deny he did it.

To prosecutors, however, post traumatic stress disorder is a lame excuse.

``It is a way to attempt to excuse responsibility for this deadly and extreme act,'' Deputy District Attorney Ronald Geltz said.

The shooting occurred after what Keech and his lawyers described as months of threatening family confrontations with Candy, a rugby-playing Englishman and contract manager at Universal Studios.

Before a gag order was issued Monday, Keech told The New York Times: ``I snapped.''

``I was afraid for my life. I thought I was back in the prison camp and I was about to be beaten to death,'' he said.

Keech said he doesn't know whether he has had any previous episodes of post-traumatic stress stemming from his 3 1/2 years in prison camps, where he saw hundreds die. He said the horrors he experienced flared the day he killed Candy because he feared for his daughter's life.

Experts said it's unlikely Keech could have kept his disorder dormant for so long without showing any symptoms. But they said anything is possible.

``We have World War II veterans who have not had any symptoms previously because they held two jobs or were doing other things to occupy their minds,'' said Robert Nicholson, psychology professor at the University of Tulsa in Oklahoma. ``But when they retired and had more time on their hands, they began experiencing symptoms.''

Keech was a purchasing agent at Rockwell International Corp. until he retired about 15 years ago.

The disorder became an official diagnosis by the American Psychiatric Association in 1980. It generally has been associated with Vietnam War veterans, but there have been cases involving Korean War and WWII veterans.

The disorder can also affect victims of rape or natural disaster or those who believe their lives are in danger, said Terri Weaver, a clinical psychologist at the Center for Trauma Recovery at the University of Missouri, St. Louis.

Symptoms include flashbacks, a numbing of the senses, angry outbursts and sleep and concentration problems. When used as a defense at trial, it often accompanies an insanity plea.

But Keech is not claiming insanity. And Candy's sister doesn't believe Keech suffers from the disorder.

``If that's the case, then why hasn't he said he's sorry?'' said Jocelyne Candy Bunyan. ``Who's going to be next? The mailman?''