EASTLAND, Texas (CN) - A state prosecutor in Texas says a jury was entitled to reject the insanity defense of the ex-Marine who killed "American Sniper" Chris Kyle and a friend, arguing against the killer's appeal for a new trial.
A jury on Feb. 24, 2015, convicted Eddie Ray Routh in the double-murders of Kyle and Chad Littlefield.
The two had befriended the troubled veteran at the request of Routh's mother shortly before the then-25 year-old riddled them with bullets at a Dallas shooting range.
Prosecutors said Routh then fled in Kyle's stolen Ford truck, made a burrito stop at Taco Bell, then drove to his sister's north Texas house, where he confessed to the double-murders.
After a nine-day trial that overlapped with the nationwide showing of the hit movie "American Sniper," it took the jury of 10 women and two men just two-and-a-half hours to reject Routh's insanity plea and convict him of capital murder.
The Clint Eastwood-directed movie, based on Kyle's bestselling autobiography of the same name, depicts the life of the storied former Navy SEAL, known to be the most lethal sniper in U.S. history.
Routh was automatically sentenced to life in prison without parole for the 2013 slayings.
But Routh's attorney say jurors got it wrong. In a December brief to the Texas 11th Court of Appeals seeking to overturn the guilty verdict, Ft. Worth attorney Warren St. John said the former Marine was insane at the time of the crimes and "did not know his conduct was wrong."
St. John also said his client is entitled to a new trial based on two rulings made by state District Judge Jason Cashon that he claims are grounds for reversal.
Erath County District Attorney Alan Nash rebuffed Routh's assertions in a 57-page brief to the state appellate court March 11.
The prosecutor argued that the overwhelming amount of evidence is sufficient to support the jury's rejection of Routh's insanity defense.
"The jury was entitled to disbelieve expert testimony diagnosing appellant with a severe mental disease or defect, and the jury could conclude that appellant knew his conduct in murdering Littlefield and Kyle was wrong," Nash wrote.
"Further, the state's evidence that appellant did not suffer from a severe mental disease or defect, appellant was intoxicated at the time of the offense, and appellant knew that his conduct was wrong supports the jury's rejection of the insanity defense."
Defense attorneys had argued that Routh suffered from schizophrenia and post-traumatic stress disorder, and that when he killed Kyle and Littlefield, he was in the grip of a psychosis "so severe that he didn't know what he was doing was wrong."
Prosecutors portrayed Routh at trial as a deliberate killer who waited for the "opportune time" to shoot the two friends in cold blood. That time came when Kyle's magazine emptied during target practice and Routh seized the moment to shoot both men in the back.
They said that Routh's behavior was caused by his voluntary intoxication on the morning of the murders. Before meeting his two victims the day of the murder, Routh drank whiskey and smoked marijuana laced with embalming fluid, prosecutors said.
They also insist Routh's defense team failed to prove that he did not know his conduct was wrong.
Routh did not testify at his trial.