Malcolm Gladwell's "Blink" has a pretty interesting section about this problem, using the shooting of Amadou Diallo by four NYC police officers as an example. In a way, it kind of made me feel for both sides of the gun. Perception can be a really tricky thing to overcome.
Somewhat related: The Martin shooting keeps making me think back to this excellent Reddit comment: http://www.reddit.com/r/politics/comments/…