Defense attorneys are set to present their first full day of testimony Wednesday in the trial of a former Marine accused of fatally shooting "American Sniper" author Chris Kyle and another man.

Prosecutors rested their case Tuesday. Attorneys for Eddie Ray Routh called his mother as their first witness. Jodi Routh testified that she did ask Kyle to help her troubled son but that she didn't know he would take Routh to a shooting range.

Prosecutors asked the mother if she regretted not telling Kyle of threats Routh had made to kill himself and his family.

"I was just looking for help for my son," she responded.

Kyle, the famed former Navy SEAL sniper who served four tours in Iraq, and his friend Chad Littlefield were shot dead at the range in February 2013.

Eddie Ray Routh has pleaded not guilty, and his attorneys are mounting an insanity defense. Family members have said he was suffering from post-traumatic stress disorder after serving in Iraq and in Haiti after the devastating 2010 earthquake.

The trial has drawn intense interest, partly because of an Oscar-nominated film based on Kyle's memoir.