There are a huge number of people who have been mentally ill at one time or another and some probably fake it for attention or to claim disability payments.

Judges could put in some kind of a block into the Federal database for those that should not be able to buy guns based on the history of a person. Still very imperfect as there was that former law enforcement officer near Tampa who shot a man because he threw popcorn at him. Movie theater shooting: Judge denies 'stand your ground' defense - CNN.com That hardly sounds rational.