Defense attorneys claim Andrew Brannan was suffering from post-traumatic stress and bipolar disorder . The defense says the former Marine suffered a traumatic brain injury in Iraq that left him unable to distinguish reality from fantasy. He killed Deputy Kyle Dinkheller , 22 , in 1998 ; YouTube videos show the deadly confrontation .
Defense attorneys claim Andrew Brannan was suffering from post-traumatic stress and bipolar disorder . Brannan is scheduled to be executed at 7 p.m . ET Tuesday in Georgia . He killed Deputy Kyle Dinkheller , 22 , in 1998 ; YouTube videos show the deadly confrontation .