Moved by a huge tide of troops returning from Iraq and Afghanistan with post-traumatic stress, Congress has pressured the Department of Veterans Affairs to settle their disability claims - quickly, humanely, and mostly in the vets' favor.  The problem: The system is dysfunctional, an open invitation to fraud. And the VA has proposed changes that could make deception even easier.

PTSD's real but invisible scars can mark clerks and cooks just as easily as they can infantrymen fighting a faceless enemy in these wars without front lines. The VA is seeking to ease the burden of proof to ensure that their claims are processed swiftly.

But at the same time, some undeserving vets have learned how to game the system, profitably working the levers of sympathy for the wounded and obligation to the troops, and exploiting the sheer difficulty of nailing a surefire diagnosis of a condition that is notoriously hard to define.

"The threshold has been lowered. The question is how many people will take advantage of that," said Dr. Dan G. Blazer, a Duke University psychiatrist who has worked with the military on PTSD issues. PTSD, he adds, is "among the easiest (psychiatric) conditions to feign."

Some claims are built on a foundation of fake documents; in other cases, the right medals - plus a gift for storytelling - secure unearned benefits. Consider:

• Gulf War veteran Felton Lamar Gray told a VA psychologist he was spattered with "blood and chunks of head" when his "best friend" was shot in the face in Iraq. But only after the VA rated Gray 100 percent disabled did anyone check into his stories - and discover the comrade he spoke of is very much alive.

• Vietnam-era veteran Keith Roberts of Gillett, Wis., said he was traumatized when he was prevented from rescuing a friend being crushed under a Navy airplane, and was eventually granted 100 percent disability. But when the case was reopened, investigators could find no evidence that Roberts was even present when the accident occurred.

Of the roughly 1.6 million troops who have served in the war zones of Afghanistan and Iraq, more than 134,000 had been seen at VA health care facilities for "potential PTSD" as of late last year, according to a government report.

Researchers suggest the numbers of actual sufferers are much higher.

Last year, U.S. Rep. John J. Hall, D-N.Y., introduced legislation to streamline the VA claims process, especially for veterans in traditionally noncombat roles. Arguing that the system failed to recognize the changing face of war, Hall said the claims process had become an obstacle to healing, "inflicting upon the most noble of our citizens a process that feels accusatory and doubtful of their service."

VA Secretary Eric K. Shinseki responded last summer with a proposed rule change. Until now, the agency has required independent proof that a traumatizing event - or "stressor" - occurred. Under the proposed changes, a veteran's "lay testimony" about what happened to him would suffice, as long as it "is related to the veteran's fear of hostile military or terrorist activity" and is "consistent with the places, types, and circumstances of the veteran's service."

Already, VA officials are legally bound to resolve "any reasonable doubt" in the veteran's favor.