Transcript for 'American Sniper' Trial Defense Makes Its Case
And now to Texas tonight, the "American sniper" trial. This evening, the family of the accused killer, on the stand. Arguing the former marine, seen here, accused of killing Chris Kyle, did not know what he was doing was wrong. The transformation to that day in the back of the police cruiser. Tonight, his girlfriend describing his behavior in the days before the murders. ABC's Ryan Owens in Texas. Reporter: She was closer to the kill earl than anyone else in the months leading up to the crime. And Eddie routh's girlfriend may have done more to help his insanity defense than any witness yesterday. Jennifer wield has a degree in psychology and met routh through a dating website the year before he killed "American sniper" Chris Kyle and Chad Littlefield. She argued with routh the morning of the murders. The night before, she says, he was paranoid and hadn't showered in weeks. "They are listening to us," he told her, and asked her to write down her thoughts so the government wouldn't hear them. Weed also told the jury that two weeks before, routh held her and a roommate hostage with a decorative ninja sword and a butch er knife. He told her, "People were out to get us. We needed to stay in the apartment." Routh was arrested and put back in a mental hospital. Eddie routh's sister testified about her little brother's history of erratic behavior. She recounted that he visited her and her husband. They called 911. Listen, my broerl just came by here. He told me that he's committed a murder. Reporter: Before he left and led police on this high speed chase, she told her brother, "I love you, but I hate your demons." They say justice is southwest here in Texas, and this case is moving fast. The judge says testimony could end as soon as Friday, then closing arguments Monday. David? Ryan Owens tonight. Ryan, thanks.
This transcript has been automatically generated and may not be 100% accurate.