Should post-traumatic stress disorder be a defense for murder? Watch "War Rage on Trial" on CNN Presents, Sunday, May 6 at 8 p.m./11p.m. ET.
Altoona, Pennsylvania (CNN) -- Raymond Williams had just retired and was looking forward to traveling out west with his wife and spending time with his three grandchildren. But all those plans were shattered on April 6, 2009. As Williams, 64, went to get the mail on that spring day, he was gunned down by a man he'd never met.
His wife found his body.
"She said, you know 'Matt! Matt! Somebody shot Dad,'" recalled Williams' son, Matt. "It didn't register. I'm thinking, 'OK where is he now? Did they take him to the hospital? What hospital is he in?' And before I could even get another word out, she goes 'And he's dead.'"
A short time earlier, the same gunman had killed a teenager and wounded a woman at a store in the same working-class town of Altoona in central Pennsylvania.
The gunman, Nicholas Horner, was a husband, a father, and a veteran soldier who had been awarded multiple medals for his service in Iraq, including a combat action badge. Less than a year after returning from combat, Horner faced two first degree murder charges and the possibility of the death penalty.
"Not in a million years could I believe this was true because Nick would never, he could never hurt anyone," said Horner's mother, Karen. "I know Nick. Nick pulled the trigger, but that wasn't Nick."
After he returned from Iraq, Horner was a different person, his mother said. He barely left his home and, oftentimes, his wife would find him crying in the corner of the basement.
"He wasn't my little boy anymore," said Karen Horner. "You could see in his eyes, he had seen things and done things that probably none of us should ever see."
There was no question that Horner had committed the crime, and his attorney would not argue otherwise. The question was whether Horner was to blame.
"I argued to the jury in my opening (statement), I said I believe that the Iraq war came home that day," said defense attorney Tom Dickey.
Horner was one of the thousands of soldiers and veterans diagnosed with post-traumatic stress disorder after returning from fighting in Iraq or Afghanistan. In total the military says 90,000 currently serving troops who fought in those wars were diagnosed with PTSD. The number from the Veterans Administration is well over 200,000.
After a decade of combat, PTSD is being used as a criminal defense in the courtroom. Horner's case would test whether this combat-related illness could be accepted as a defense for murder.
The morning of the shootings, Horner dropped his kids off at school and went shopping with his wife. An argument ensued and he stormed away, armed with his .45-caliber handgun.
"He left Walmart and went to a bowling alley, where he sat all afternoon and drank several ... at least two pitchers of beer," said prosecutor Jackie Bernard.
Horner ordered food, talked to people and then walked over to the Subway sandwich shop intending to rob it, the prosecutor said.
Witnesses said Horner pounded on the shop's back door trying to get in. Evidence showed that Horner cut the electrical wires to the restaurant and even tried to shoot out the utility box.
Horner's lawyer argues he was in the middle of a PTSD episode and, to him, the Subway looked like a building in Iraq.
"Why do you in broad daylight enter from the rear and announce yourself by firing, you know, five or six shots?" Dickey said.
Once inside, Horner shot and killed Subway worker Scott Garlick, a teenager two months shy of graduating high school. He then shot and injured another worker, Michelle Petty, and stole about $130.
"And when he left, he walked over to Scott's body as he lay bleeding there and said to him: 'Sorry, I didn't wanna have to do that to you,'" said Bernard.
Several blocks away, Horner spotted Raymond Williams. Prosecutors argue he killed Williams for his car keys to try to get away.
During the trial Horner pleaded "diminished capacity" in an effort to persuade the jury to find him not guilty because of PTSD.
PTSD on trial
The same year as the Altoona shootings, an Oregon jury found Iraq war veteran Jessie Bratcher guilty of murder but legally insane. So, instead of serving 25 years in a maximum security prison, Bratcher was provided treatment at the Oregon State Hospital. . A medical review board keeps track of his progress, and his attorney says he could be released as early as this month.
"I can honestly tell you that I would have never shot anybody if it hadn't been from PTSD," Bratcher said.
The ex-soldier got into a shoving match with a man who he believed raped his girlfriend. The argument ended with Bratcher unloading six hollow-point bullets into victim Jose Medina, killing him.
"I remember him threatening and pushing me, then having flashbacks of Iraq ... like seeing my buddy get killed in Iraq," Bratcher said.
From the moment he set foot in Iraq, Bratcher said he was bombarded by rockets and mortars. When he returned, he had trouble sleeping, couldn't hold a job, and was behaving unusually.
"I remember his sister said that once she looked out the window, and he was in the backyard working in the garden and he had his AK-47 slung over his shoulder," said Markku Sario, Bratcher's attorney. Bratcher would live out in the woods for weeks at a time and set up perimeters that he could defend, Sario said.
Like the Horner case, there was no question that Bratcher killed the victim. Bratcher had turned himself in to authorities after the shooting.
"There was no defense to the action," said Sario. "The only defense that was possible was either good negotiation -- but we had a district attorney who wasn't interested in negotiating -- or some sort of mental defense."
A PTSD diagnosis has helped Iraq and Afghanistan veterans win acquittals of lesser crimes like robbery, and has reduced prison terms for others. But Bratcher's attorney said this case represents the first major criminal exoneration linked to PTSD since the Vietnam war. The defense had been used with some degree of success in the years following that war.
"It's not a defense that has been written up a lot. It hasn't been used a lot," said Sario.
But that's changing. Now defense attorneys are advertising their expertise to troops facing charges, with hooks like "Criminal Defense Lawyers for Veterans with PTSD."
One veterans' group, the National Veterans Foundation, is creating a manual on how to defend veterans with PTSD -- detailing tips like finding witnesses from the defendant's squad. Such a witness "can testify as to the horrific events that the defendant has gone through, because those are the things that sell to a jury," said Sario, who also is helping compile NVF's manual.
Not an easy defense
Currently, the crime rates associated with Iraq or Afghanistan veterans diagnosed with PTSD are not tracked. But a 1988 study of Vietnam veterans could provide a glimpse into what is to come as more veterans return from these wars.
About 480,000, or just over 15%, of all Vietnam veterans included in a National Vietnam Veterans Readjustment Survey done about a decade after the war were diagnosed with PTSD. Of those diagnosed, about half had been arrested or jailed at least once (34% more than once) and 11.5% had been convicted of a felony, according to the survey.
Today, many in the criminal justice system are reporting an increase in cases involving war veterans suffering from PTSD.
"Presently I'm swamped with cases, and they've been increasing," said William Brown, a criminal justice professor at Western Oregon University who testifies as an expert witness. "We haven't begun to see the wave of all this."
With no concrete statistics available, Brown bases his forecast off of his own caseload and studies he's done at the Marion County jail system in Oregon. Marion County is one of the few places where those in jail are asked their veteran status.
"There's no structure available right now to even quantify it," he said.
But if a PTSD defense is used inappropriately, a judge and jury might see it as making an excuse and the defense may backfire.
"If you try to shoehorn it inappropriately, it is not received well," said Dr. Landy Sparr, director of the forensic psychiatry training program at Oregon Health & Science University.
Sparr, who has expertise in mental incapacity defenses, said PTSD is not an easy defense to use and cautions against the idea that there will be an epidemic of these cases.
"PTSD as an insanity defense in a murder case is hard to use because the person knows the difference between right and wrong," said Sparr. "They are not delusional or psychotic. For example, they do not believe they have killed a Martian instead of a human."
And Sparr adds that, depending on the state's law, the other issue may be whether or not the defendant could have controlled his or her behavior.
"In either case, you usually have to prove that the defendant was in the throes of a flashback when committing the crime," said Sparr.
The issue of PTSD as a defense for murder could come up when U.S. Army Staff Sgt. Robert Bales faces court martial for 17 counts of murder stemming from a a bloody massacre in Afghanistan. The March 11 rampage strained already tense U.S.-Afghan relations. Bales' attorney has indicated he intends to raise the issue of his client's mental state during the upcoming trial.
Nick Horner's mother says that after he returned from Iraq, her talkative son didn't mumble more than a few words.
"Everything started to change ... the phone calls got less and less, the conversations got shorter," said Karen Horner. "He would have to have a weapon with him constantly to feel safe and secure. The doors were always locked in his home. He couldn't go into public without having panic attacks."
Nick Horner's lawyer argued he was confused by a mix of prescription drugs used to treat PTSD.
"That's what I've been trying to argue throughout, is that Nick is sick and not evil," said Dickey
The prosecutor, however, told jurors those drugs did not impair Horner's judgment.
"He had the ability to form the specific intent to kill. And he did have the intent to kill when he shot Scott and Mr. Williams," said Bernard.
In the end, three medical experts agreed with the prosecution and so did the jury. PTSD was not a sufficient excuse for murder in this case.
"I understand that Mr. Horner saw things in Iraq that were probably horrifying, but you know, so did we. One thing I know that he didn't see was the image of his father, you know, laying on the asphalt in a pool of blood like my mother saw," Matt Williams said.
Nick Horner was convicted of first-degree murder. The jury couldn't agree on the death penalty so he got life in prison.
"We all feel like we're doing a life sentence with Nick right now," said Karen Horner. "It's still a nightmare we can't wake up from."