The PTSD defence is in public consciousness after the arrest of US Staff Sergeant Robert Bales, accused of murdering 16 Afghan civilians.
Bales was said to be under severe emotional and mental strain after three Iraq deployments and had received a minor traumatic brain injury during a vehicle roll-over. Afghan villagers believe the shootings were revenge for a bombing.
Bales also has financial problems and owes US$1.5 million ($1.85 million) after defrauding an Ohio couple in 2000 shortly before he joined the army.
His lawyer, John Henry Browne, said Bales suffered from PTSD caused by repeated combat tours and the brain injury. Browne said his client had "diminished capacity".
Other crimes have also thrust PTSD into the headlines. In December, Benjamin Colton Barnes shot and killed a park ranger at a roadblock in Mt Rainier National Park.
Barnes had previously shot and injured four people at a party and used an assault rifle to hold off a pursuing SWAT team. Barnes, who had served in Iraq, was later found dead.
Last July his mother, Nicole Santos, had sought a restraining order.
"I think it is important for the court to know that Benjamin was also deployed to Iraq in 2007-2008 and has possible PTSD issues," she wrote. "He gets easily irritated, angry, depressed and frustrated." She said he had threatened suicide and kept an arsenal of guns.
And last week Abel Gutierrez, an Iraq veteran, was said to have "just snapped" before killing his mother, his 11-year-old sister and himself in Gilroy, California.
Gutierrez had endured post-war nightmares and his family suspected PTSD.
"He said he killed a lot of people in Iraq," a family member said. "It was on his conscience, and he didn't want to live any more."
The US Department of Veterans Affairs (VA) has tried to counter media claims of veterans with PTSD "running amok".
A blog posted by Kate Hoit, a VA public affairs officer, cautions against an "inaccurate media narrative" that rehashes the crazed Vietnam vet beloved by Hollywood.
She cites Dr Sonja Batten, the VA's deputy chief consultant for specialty mental health: "The truth is, PTSD doesn't have to, and shouldn't, impede success in everyday life for veterans," says Batten. "Years of research have demonstrated ... that most people recover naturally after potentially traumatic events, and we have effective treatments for those who develop more significant problems with PTSD."
But many veterans may struggle to accept this upbeat prospect. On average, 18 veterans attempt suicide each day. Some 300,000 are homeless. And 35 per cent are unemployed.
While PTSD may not absolve Bales or Ocampo, the diminished capacity defence points to a looming problem, as America wakes up to a costly legacy bequeathed by the nation's decade-long wars. Last June a Brown University study put the bill for the Iraq and Afghanistan conflicts at US$3.7 trillion, rising to US$4.4 trillion. A big chunk of this will be long-term health costs as veterans, their families and communities deal with PTSD and other mental issues.
Soldiers have always experienced PTSD - once known as "combat fatigue" or "shell shock" - but it was not recognised as a mental disorder by the American Psychiatric Association until the 1970s, when some 830,000 US Vietnam War veterans, or 30 per cent of the total, endured this trauma.
But the lethal legacy of the war on terror may prove more intractable. Some 300,000 US Iraq and Afghanistan veterans - 19 per cent of the 1.64 million deployed until January 2008 - have PTSD or acute depression, according to a 2008 Rand Corporation monograph, Invisible Wounds of War.
As well, about 320,000 soldiers had a "probable" traumatic brain injury, (TBI), while 5 per cent had a TBI as well as PTSD and depression.
"Unlike the physical wounds of war that maim or disfigure, these conditions remain invisible to other service members, to family members, and to society in general," it said.
"All three conditions affect mood, thoughts, and behaviour; yet these wounds often go unrecognised and unacknowledged ..."
Many brain injuries are caused by improvised explosive devices, or IEDs. Some soldiers survived multiple IED attacks. While speedy evacuation and field surgery saved many victims, the effect of an IED's violent concussive effect over time remains unclear.
Such explosions trigger a rapid change in pressure, causing the brain to expand and contract inside the skull. This may cause molecular changes that affect the brain's frontal lobe, which controls our emotions.
"What's interesting about blast-related concussion is that it affects the region of the brain that is implicated in anxiety disorders and mood disorders," said Navy Commander Greg Caron, a psychiatrist.
Soldiers who return from deployment abroad must declare any health problems, such as being unable to sleep or other PTSD symptoms. But soldiers who want to leave the military have no incentive to report conditions that may keep them there.
Then there's the cost to taxpayers. In February the Congressional Budget Office found almost all soldiers with PTSD and brain injuries require far longer VA care than other wounded veterans.
Out of some 500,000 soldiers seen by the VA for health issues, 103,500 [21 per cent] had PTSD, 8700 [2 per cent] had TBI, and 26,600 [5 per cent] had both conditions.
The Rand Corporation believes the cost of treating these is "substantial" - US$4 billion to US$6.2 billion for PTSD and depression and US$591 million to US$910 million for TBI, both over two years in 2007 dollars - while social scars include homelessness, alcoholism, drug addiction, domestic violence, failed relationships, unsafe sex and suicide.
Then there's reduced workplace productivity. No one knows what this will be, but the Rand report warns the true cost of both wars may have been "significantly understated".
Ominously, the report says "widespread" mental health and cognitive conditions among veterans "represent the primary type of morbidity in coming years".
Nonetheless, a few hopeful signs point to a better future.
A few miles east of Camp Pendleton, a sprawling US Marine base in San Diego County, a unique experiment is helping veterans return to the workforce.
Archi's Acres, a small organic farm run by Colin and Karen Archipley, is part of a US movement to turn swords into ploughshares.
As elderly farmers retire, the Archipleys, and others like them, hope to give veterans purpose and stability by training them as replacements in an echo of the Anzac soldier-settler schemes.
Archipley, a former Marine Sergeant, says the US lacks a "transitioning" agency to help soldiers adjust to a civilian environment. Farming may be a good place to start.
War trauma
300,000
US Iraq and Afghanistan veterans - 19 per cent of the 1.64 million deployed until January 2008 - suffer from post traumatic stress disorder (PTSD) or acute depression according to a 2008 Rand Corporation monograph, Invisible Wounds of War.
320,000
soldiers experienced a "probable" traumatic brain injury [TBI], while 5 per cent suffered from a TBI as well as PTSD and major depression.
US$4 billion
Cost of PTSD to America War trauma
