February 11, 2015 7:39 AM EST

Behind barricades and 24-hour-a-day security, 12 men and women in the small town of Stephenville, Texas, on Wednesday will begin hearing the murder case against the ex-Marine who shot and killed Chris Kyle, the Hollywood-certified hero of the box-office smash American Sniper.

Eddie Ray Routh, 27, has already admitted that he killed Kyle and a friend, Chad Littlefield, two years and nine days ago at a gun range. But what the jurors will consider is whether he committed capital murder or whether he’s not guilty by reason of insanity.

Here’s a guide to what will be one of the most closely watched trials of the year…

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