Judge Andrew Napolitano weighed in this morning on some of the key factors surrounding the Chris Kyle murder trial.

The jury was seated Monday in the trial of Eddie Ray Routh in Texas. Routh, 27, is said to have struggled with PTSD after leaving the Marines in 2010. 

He is accused of fatally shooting Kyle and another man at a gun range two years ago. 

In choosing the 10-woman, two-man jury, the judge refused to rule out those who had read Kyle's book or seen the movie.

Instead, jurors were asked if they could put that information aside and fairly evaluate the case.

The judge explained that defense attorneys will be trying to prove that Routh was so mentally ill that he didn't know what he was doing.

He said in Texas, the defense has the "affirmative obligation" to prove Routh was insane and actually thought he was shooting at the Taliban when he committed the killings.

"The question is what was in his head. The whole case is what lawyers call a 'swearing match between experts,'" said Napolitano.

The other factor is the defense position that Routh cannot get a fair trial due to the huge popularity of "American Sniper."

The judge rejected motions to delay or move the trial due to the recent release of the hit movie. 

Napolitano said some prosecutors would probably welcome a delay, since the publicity of the movie will likely be the basis for an appeal if Routh is found guilty.