The best "what if" scenario is that the criminal is unarmed. He's got his hand in his pocket faking a gun. Then the victim can pull out his real gun and yell "Surprise! I have a real run gun and you just have a finger pointing at me!"I just don't know about the surprise portion. I can't see it working. Can those that believe you lose the surprise aspect give your best " what if " scenario.
Worst case scenario, the criminal does have a gun or a knife and then it's a matter of a quick-draw shoot out just like in the old west. Except the criminal has already drawn his weapon.
The problem with the "element of surprise" is that it is strictly a tactic to enhance the effectiveness of an attack and has no deterrent value. If a person is in a self defense position that warrants using the gun, the criminal already has used the "element of surprise" to gain the upper hand against the target. Using the "element of surprise" against a criminal that ALREADY has gained the advantage is brave at best and a deadly mistake at worst.