Stephenville, Texas (CNN)The trial of the man accused of killing Chris Kyle, the protagonist in the top-selling book and hit movie "American Sniper," began Wednesday with a lawyer using Kyle's own words to bolster an insanity defense. Eddie Ray Routh is accused of killing Kyle and Kyle's friend, Chad Littlefield, at a firing range at Rough Creek Lodge, about 90 miles southwest of Dallas on February 2, 2013. In his opening statement, defense attorney Tim Moore read a text Kyle sent to Littlefield about Routh as the three men rode in Kyle's pickup truck to the range. "About an hour and a half into the drive, Chris Kyle was sitting in the driver's seat and he texts Chad Littlefield sitting right next to him. He texts, 'This dude is straight-up nuts,'" Moore said. "Chad Littlefield texts Chris Kyle back, 'He's right behind me, watch my six [military lingo for 'watch my back.']. So while we don't know what the conversation was, we do know what Chris Kyle was thinking at the time he was in that truck."
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Defense lawyer: Chris Kyle described accused killer as "straight-up nuts" in a text
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Eddie Ray Routh is accused of killing Chris Kyle and another man at an isolated outdoor firing range
Routh shot Kyle five times in the back and side and once in the side of the head, using a .45-caliber pistol, and shot @placeholder with a 9 mm pistol four times in the back, once in the hand, once in the face and once in the head, Nash said.