STEPHENVILLE, Tex. — Could it have been post-traumatic stress disorder?

The closer this rural town gets to the murder trial of Eddie Ray Routh, the more the question comes up. The Marine Corps veteran is accused of killing two men who were trying to help him at the time: former Navy SEAL Chris Kyle, whose life forms the basis for the blockbuster movie “American Sniper,” and his friend, Chad Littlefield. Police said Routh shot Kyle and Littlefield on Feb. 2, 2013.

Routh, now 27, later confessed to the killings, police said. It is widely believed that his defense team will pursue some form of insanity plea, perhaps citing post-traumatic stress and his time in the military as a reason for his actions. His family members have said repeatedly that he was diagnosed with post-traumatic stress, raising concerns among combat veterans that the case will perpetuate stereotypes about the condition.

His brother-in-law, Gaines Blevins, told police in a 911 phone call shortly after the killings that he had been recently diagnosed with it, and his aunt later told a TV station that he had it.

“It is PTSD. Definitely, that’s what caused it,” said the aunt, Sundae Hughes. “That’s not Eddie. That’s not who he is.”

It’s unclear what factors might have contributed to Routh’s actions. But his military record, released to The Washington Post, does not indicate he was engaged in direct combat.

He joined the Marine Corps in June 2006 and served four years as a small arms repairer/technician, a job that primarily involves working in an armory on rifles and other weapons. He served in Iraq between September 2007 and March 2008, aboard the amphibious assault ship USS Bataan from May 2009 to December 2009, and then in support of earthquake relief operations in Haiti from January through April of 2010.

Routh did not receive the Combat Action Ribbon, the Navy Department decoration that recognizes those who “directly and actively participate in ground or surface combat,” as the Navy and Marine Corps Awards Manual indicates. Marines and sailors can get it a variety of ways, including engaging in a firefight, facing direct exposure to an improvised explosive device detonation, and participating in a clandestine mission in which they are restricted in their ability to return fire even though it is likely that they will be attacked.

There are factors besides combat that have been shown to contribute to post-traumatic stress, such as experiencing a disaster or being the victim of a crime.

The discussion of whether Routh suffered from PTSD has been regular fodder on military blogs and on talk radio shows in recent days, including in Texas. One veterans group, the Warfighter Foundation, has said that Routh served in Iraq at Balad Air Base, and was far away from combat, citing Marine sources.

As noted in this Dallas Morning News piece, Routh had been in and out of Green Oaks Psychiatric Hospital in Dallas at least twice in the five months before Kyle and Littlefield were killed. The facility treats adults with conditions including suicidal thoughts, depression, psychotic thinking and bipolar disorder.

Routh had previously threatened to kill himself and his family, the Dallas Morning News reported. The Daily Mail of Britain, citing an interview with Routh’s father, also reported that the Marine veteran spent three weeks in a Department of Veterans Affairs hospital in Dallas after having an episode near a lake.

“He was talking just as calm as you and me talking now but he was gone, in his eyes he was gone. I had a .357 pistol and I pulled it away from him three times. He kept going for it and saying he would hurt himself,” the father said. “The third time, I emptied all the bullets and threw them in the lake.”

Editor’s note: Checkpoint is on assignment this week in Texas, covering the murder trial of Eddie Ray Routh, a Marine Corps veteran who is accused of killing former Navy SEAL Chris Kyle, the author of “American Sniper,” and his friend Chad Littlefield.