Fort Hood base attack: Major Nidal Hasan to go on trial
6 August 2013 Last updated at 07:15 BST
The military trial of a former US Army psychiatrist who killed 13 and injured more than 30 in a 2009 shooting rampage at a Texas army base begins on Tuesday.
Major Nidal Hasan, who is defending himself, has admitted the killings, but argues he was protecting Muslims and the Taliban in Afghanistan.
However, a military judge has already rejected his "defence of others" claim.
If convicted on 13 counts of murder and 32 counts of attempted murder, the 42-year-old faces the death penalty.
Nick Bryant reports.