It seems to me that many are caught up on the definition of "risk."
Risk is simply the chance or possibility of induced harm. In every case there is perceived risk and actual risk. Sometimes these coincice but many times they do not. Risk is NOT the future. Risk is a probability factor. Even an unarmed intruder is a risk until it can be determined that they pose no threat. Risk is inherent, it is the presence of an unknown. As long as there are unknowns there are risks. It is lawful for a homeowner to systematically eliminate the unknowns to eliminate risk.
In Oni's example of a mentally handicapped intruder the perceived risk is greater than the actual risk. Of course, if we take his hypothetical and pair it with Steinbeck's "Of Mice and Men," it seems that a mentally handicapped person may be of greater actual risk than perceived risk as well.
In most cases a homeowner does not know the actual risk, only the perceived risk. They may only make decisions based on perceived risk. That is why many state laws will allow deadly force if the perceived risk was great enough.
The difference between police officers and citizens is that police officers are 1). trained to perceive risk more accurately than citizens and 2). trained to eliminate risk more efficiently and with less force than citizens.
I do not own a gun. But, if I perceived enough risk to my wife and child from an intruder I'd sure as hell use any force I could until the risk was eliminated. If i could determine that the intruder was unarmed then obviously my perceived risk level would decrease and so would the level of required force to eliminate the threat. However, if i could not determine the intent of the intruder then my perceived risk remains at its highest level and thus, my level of allowable force would remain high. In other words, I am announcing my presence and if the intruder does not respond by leaving then I'm swinging my baseball bat until the perceived risk to my wife and child is eliminated.
™ Version 4.2