Man who killed 'American Sniper' Chris Kyle sent to Texas prison psychiatric unit
Eddie Ray Routh, 27, walks into court for a pre-trial motion hearing in Stephenville, Texas in this Feburary 10, 2015 file photo. REUTERS/LM Otero/Pool/Files

The man convicted last month of murdering former U.S. Navy SEAL Chris Kyle, whose best-selling autobiography was turned into the movie "American Sniper," has been transferred to Texas prison psychiatric unit, officials said on Wednesday.

Eddie Ray Routh, 27, a former U.S. Marine, was found guilty on Feb. 24 of fatally shooting Kyle and Kyle's friend Chad Littlefield multiple times at a gun range about 70 miles (110 km) southwest of Fort Worth in February 2013.

Routh was sentenced by a Texas judge to life in prison without the possibility of parole. He was transferred this week to the Jester IV unit, a psychiatric facility in Richmond, prison officials said.

Defense lawyers, who tried unsuccessfully to have Routh declared innocent by reason of insanity, said their client had been to hospitals at least four times because of his mental illness and was diagnosed as psychotic.

Prosecutors said Routh knew what he was doing when he killed Kyle and Littlefield and called a psychologist to the stand who, after examining Routh, said he had a personality disorder made worse by his heavy drug use.

Jurors at the trial in the rural city of Stephenville were instructed they could find a person innocent by reason of insanity if the defendant did not know their conduct was wrong due to a severe mental defect or illness.

As a sniper in Iraq, Kyle reportedly had 160 kills, considered the highest count in U.S. military history.

(Reporting by Jon Herskovitz; Editing by Bill Trott)