The widow of the Navy SEAL depicted in the Oscar-nominated film "American Sniper" clutched military dog tags as she told jurors about her final moments with her husband, just hours before he and a friend were killed at a Texas gun range.

Taya Kyle was the first prosecution witness called Wednesday in the murder trial of the ex-Marine accused of fatally shooting Chris Kyle and his friend Chad Littlefield two years ago. The trial in the small town of Stephenville, located about 30 miles from the rural luxury resort where the men were killed, has attracted national attention with the recent release of the blockbuster movie based on the memoir of the sniper who served four tours in Iraq.

Defense attorneys are seeking an insanity defense for Eddie Ray Routh, 27, who faces life in prison without parole if convicted of capital murder. Kyle had taken the troubled Marine to the shooting range after Routh's mother asked Kyle if he could help him.

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Taya Kyle paused and then her voice broke when a prosecutor asked her to give jurors the name of the man she'd married. But her testimony was conversational and compelling and she often looked straight at jurors as she talked about him, smiling when she said he had attended Tarleton State University in Stephenville before leaving to ride broncos in the rodeo and later joining the Navy. Some of the jury members were brought to tears.

"He's such a unique person because he's so humble and kind and charismatic," she said. "Doing sniper work is really an extension of your heart."

She told jurors that as her husband left to go to the shooting range on Feb. 2, 2013, "we just said we loved each other and gave each other a hug and kiss, like we always did."

The day started like any typical Saturday for the Kyles. As parents of an 8-year-old boy and 6-year-old girl, they had spent their morning cheering at youth sporting events and chatting with friends. Taya Kyle had plans that afternoon to take their daughter to a Build-A-Bear Workshop.

Taya Kyle said she'd called her husband midafternoon -- around the time he arrived at Rough Creek Lodge and Resort -- and noticed he was unusually terse. Instead of his usual "hello babe," he gave a quick "hello." He said it would be fine to have dinner with friends. Then she asked if he was OK. He just said "yep."

"It was short, like: `I wish I could say more,"' she said.

During opening statements, a defense attorney revealed a text message exchange between Chris Kyle and Littlefield as they drove to the lodge with Routh, whom Kyle had picked up at his house.

Kyle texted Littlefield: "This dude is straight-up nuts."

"He's (sitting) right behind me, watch my six," Littlefield texted back, using a military term for watching one's back.

As dinnertime approached, she became concerned. Littlefield's wife called her, also worried. Taya Kyle's alarm grew when she texted her husband: "Are you OK? I'm getting worried." There was no reply.

The bodies of Littlefield and Kyle were found at the shooting range at about 5 p.m. Both were shot multiple times.

Erath County District Attorney Alan Nash described Routh as "a troubled young man" who on the morning of the killings numbed himself with marijuana and whiskey. He said a history of mental illness should not absolve Routh in the deaths.

"The evidence will show that mental illnesses, even the ones that this defendant may or may not have, don't deprive people from being good citizens, to know right from wrong," Nash said.

Tim Moore, an attorney for Routh, said Kyle and Littlefield's text exchange shows how Routh was spiraling out of control. He told jurors that Routh was suffering from severe mental strain that day and thought he needed to kill the two or they would turn on him.

Routh was a small arms technician who served in Iraq and was deployed to earthquake-ravaged Haiti before leaving the Marines in 2010. Authorities say that after the shootings, Routh drove to his sister's house in Kyle's truck, admitted to the killings and told his sister "people were sucking his soul."