FLAGSTAFF, Ariz. - The phone roused Terry Clark from sleep. ''Flagstaff Police Department,'' a voice announced, asking to speak with Mr. Clark. Terry nudged Dave and handed over the receiver. ''My son's truck?'' she heard her husband say. ''Gentry?''
Gentry was the oldest of their three children. Had he been in a wreck? Terry crawled from bed and headed for the front door to see if her son's Toyota pickup was in the drive. She stepped out onto the porch, then stopped dead in her tracks.
In the dim glow of dawn, she could see that Gentry's truck was gone. Where it should have been, men in helmets stood clutching guns aimed at Terry's head. ''Get against the garage!'' one shouted.
At first, investigators told Terry only that a policeman had been shot.
She would hear a name, Officer Jeff Moritz, and discover he was called to their neighborhood after residents reported a pickup circling, blaring loud music. The policeman had pulled the truck over and called in the license plate, then radioed dispatch once more: ''999. I've been hit. 999. I've been hit.''
The pickup - her son's pickup - sat abandoned next to the sidewalk where, Terry soon learned, the police officer had died.
She realized then that her son was the prime suspect. Not Gentry, who had been at home in bed.
Her middle son. Eric.
The one who had been a star football player and a good student with dreams.
The one who just two months earlier called his own mother and father aliens.
Suspect's profile: The victim of the June 21, 2000, shooting was the only police officer ever killed in the line of duty in this mountain community north of Phoenix. He was a caring cop who cut firewood for the handicapped, a husband and father with one young son and a second on the way.
The accused was a 17-year-old high school senior who had a history of marijuana use and had been arrested two months earlier for drunken driving and drug possession after police found two dozen hits of LSD in his car.
A portrait emerged of a drug-crazed teen. But as the facts slowly surfaced, so did a different picture of Eric Michael Clark - that of a decent boy who had descended into a world of delusion, the terrifying existence that is schizophrenia.
It took three years for Eric Clark to be found competent to stand trial and participate in his defense. When the case proceeded, his lawyers pushed for a verdict of ''guilty except insane,'' meaning incarceration in a psychiatric facility. Instead, a judge found him guilty of first-degree, intentional murder and sentenced him to life in prison.
On Wednesday, the U.S. Supreme Court is to take up the case of Clark v. Arizona and the issue of just how difficult states can make it for criminal defendants to prove insanity.
It's the first time the court has dealt with a direct constitutional challenge to the insanity defense since lawmakers around the country imposed new restrictions following John Hinckley's acquittal by reason of insanity in the 1981 shooting of President Reagan.
The issue is determining under what circumstances absolution of a criminal act is warranted.
Increasing symptoms: Terry Clark wonders, now, when it all started.
Did it begin with Eric's fear of drinking tap water? It was December 1998, and a house fire forced the family to live temporarily in an apartment. Eric, then 16, worried about lead poisoning and would only drink bottled water.
Was that the first clue?
Always low-key, Eric then began to grow moody - exploding one minute, sobbing the next.
Was that illness or teen angst?
Terry, a school nurse, had seen her share of troubled kids. She wondered if Eric was on something, but she'd had him drug-tested before, and the results were negative. Was it depression? Anger management? The pieces didn't fit into one neat puzzle, and Eric's behavior grew more bizarre.
On June 21, 1999, Terry and Dave had their son admitted to a mental health center. He'd abandoned his car in a road, called a police officer rude and then reeled on his father, using the f-word. At the center, Eric tested positive for marijuana. But doctors thought his behavior perhaps stemmed from pre-schizophrenia. With no mental illness on either side of the family, Terry pushed that idea aside.
The family attended counseling sessions, and Eric seemed to improve. He promised Terry he'd quit using drugs and continue seeing a therapist. She had him discharged after only three days.
''He's getting better,'' Terry convinced herself.
He got worse.
That fall, Eric quit school. He became obsessed with Y2K and charged $1,700 worth of survival gear on his dad's debit card. When Jan. 1, 2000, came and went, Eric was thrilled and went back to school.
''He's getting better,'' Terry thought again - until Eric started mentioning ''them.''
''They're after me,'' he'd tell his mother.
That April, in the midst of conversation, Eric referred to his mother and father as aliens. ''If you'd go get some tools,'' he told them matter-of-factly, ''I'd show you.'' Terry was relieved when, that same month, Eric was arrested on drunken driving and drug charges; she thought that would lead to help. But authorities decided to postpone prosecution until Eric turned 18 later in the year.
On June 19, 2000, Eric called his mother an alien again.
''How would you like to be me,'' he said, ''and never know who your real mother is?''
The next day, Eric seemed better, and he, Terry and Dave went to a movie together. Afterward, Eric asked if he could stay to watch another film. He hugged his folks, and said goodbye.
Unknown motive: Investigators surmise that sometime after 1:30 a.m. on June 21, 2000, Eric made his way home, sneaked into his brother Gentry's bedroom, took his keys and left in Gentry's truck.
What happened after that, and why, no one can know for certain; Eric's never talked about it.
Both sides, and their mental health experts, agreed that Eric suffered from paranoid schizophrenia and was mentally ill.
But legal insanity is another matter; Arizona law spells out its qualified use as a defense.
''A person may be found guilty except insane if, at the time of the commission of the criminal act, the person was afflicted with a mental disease or defect of such severity that the person did not know the criminal act was wrong,'' the law states.
The prosecutor, Assistant Attorney General David Powell, argued Eric did know. One witness testified that weeks before the shooting, Eric mouthed off about his disdain for cops and wanting to shoot them. Powell's theory was Eric lured Moritz to the scene by playing loud music until residents reported him.
''He wanted to kill an officer that day,'' Powell said at trial. ''And he did.''
Defense lawyers insisted Eric's psychosis was so severe he was incapable of hatching such a plan. They noted that after the shooting, Eric called his parents from jail and explained that Flagstaff was a ''platinum city'' inhabited by 50,000 aliens. He told them: ''The only thing that will stop aliens are bullets.''
In his appeal to the U.S. Supreme Court, defense lawyer David Goldberg asserts that Arizona law is so restrictive that it violates a mentally ill defendant's right to a fair trial. For one, he says, Arizona law prohibited the trial court from considering Eric's mental illness in weighing whether he intentionally killed a police officer.
The Supreme Court could establish a more specific definition of legal insanity or allow for broader discretion in determining when evidence of mental illness may be considered at trial.
Its decision could also mean a retrial for Eric, something the Moritz family would see as unjust.
''To say, gee if you're mentally ill you can be forgiven for murdering somebody, you're giving a license to kill to millions of people,'' says the victim's father, Dan Moritz.