Hello group. Here is my opinion on the question.
Outside the home do everything possible to retreat from the situation and if others are around make it visually and verbally known to witnesses and the bad guy your reluctance to participate in any type of altercation, you don’t want to be hurt and you want to leave (put your hand on your gun, discretely). If the bad guy has a weapon (knife or club) and is within 21 feet, you can shoot. Twenty-one feet is a magic number. Studies have been done that have proven that a non-athletic person can close a 21 foot gap and deliver the thrust of a knife in 1.5 seconds (
http://www.theppsc.org/Staff_Views/Tueller/How.Close.htm). Having spent some time with local Sheriffs deputies, they confirm this and say that 21 feet is the edge of the safety-zone. Three factors must be in-play before using deadly force. Ability (weapon), Opportunity (within 21 feet) and Jeopardy (you actually believe this person is going to kill you or cause grave bodily harm and this threat is immediate and unavoidable). On the street, never point your gun unless you actually plan on firing; un-holster if you must but keep the gun low to the ground. Others can file assault charges against you if they wet their pants while you are waving your gun. Never fire a warning shot. That is TV stuff and it’s appalling that some cops do it. Firing a weapon in the direction of a human, anywhere, is the use of deadly force. Using Google, there are countless cases where warning shots by cops and civilians had no impact on the situation.
In the home, in my opinion, things are a lot different. Most home invasions happen during the day. The bad guy assumes most people will be at work. If there is a confrontation at night and in the home, the bad guy is telling you two things. First, “I don’t care if anyone is home” and second, “I am prepared to deal with the homeowners if confronted”. Now, at 2:30AM, awoken from a sound sleep to the sounds of a window breaking or door-jam splintering or just that uneasy feeling that someone is watching you sleep, are you prepared to make rational decisions regarding proper defense of your family? To issue commands, secure the area, retreat to safety (where is “safe” if not the home?), make a citizens arrest, search the bad guy for weapons or even be able to find your phone (lines cut?) to call for help. You don’t know how many bad guys there are, if they have a knife or a gun or what their real intent is. Do they want the new flat screen TV and your coin collection or do they want to tie you up and violate your wife and 9 year old daughter with various household objects while you watch helplessly? In my opinion, unless the bad guy has one foot out my front or back door, there is about a 97% chance he isn’t leaving my house alive (no warnings either). Confronted in the home, especially at night, one must conclude that the invader is prepared to use deadly force or inflict great bodily harm to accomplish whatever it was they came to do. When the cops show up after a shooting, only tell them what is apparently obvious (no details). Tell them you wish to file a complaint against the person(s) (even if dead) that attempted to kill you and that the evidence (point to the bad guy and general area) will support the statement your attorney will be making on your behalf in the morning.
Short answer: On the street run. In the home stand your ground. Only shoot to stop the threat of deadly force or great bodily harm to you or immediate family.