A former Marine sentenced to life without parole for the shooting deaths of "American Sniper" author Chris Kyle and his friend Chad Littlefield has been moved to a psychiatric prison for evaluation.

Texas Department of Criminal Justice spokesman Jason Clark says Eddie Ray Routh was transferred Monday from a prison near Abilene where he underwent initial screening about 300 miles to a prison outside Houston with more extensive medical facilities.

Clark said Thursday it's not been determined if Routh will remain at the Jester Unit prison.

Jurors last month rejected Routh's insanity defense and convicted him of capital murder for the 2013 deaths of Kyle and Littlefield. Prosecutors didn't seek the death penalty.

The case drew extra attention due to the film based on Kyle's memoir.