Here is one point of view.
Conditions of use
Each state differs with respect to the specific instances in which the Castle Doctrine can be invoked, and what degree of retreat or non-deadly resistance (if any) is required before deadly force can be used.
In general, one (sometimes more) of a variety of conditions must be met before a person can legally use the Castle Doctrine:
An intruder must be making (or have made) an attempt to unlawfully and/or forcibly enter an occupied home, business or car.
The intruder must be acting illegally—e.g. the Castle Doctrine does not give the right to attack officers of the law acting in the course of their legal duties
The occupant(s) of the home must reasonably believe that the intruder intends to inflict serious bodily harm or death upon an occupant of the home
The occupant(s) of the home must reasonably believe that the intruder intends to commit some other felony, such as arson or burglary
The occupant(s) of the home must not have provoked or instigated an intrusion, or provoked or instigated an intruder to threaten or use deadly force
The occupant(s) of the home may be required to attempt to exit the house or otherwise retreat (this is called the "Duty to retreat" and most self-defense statutes referred to as examples of "Castle Doctrine" expressly state that the homeowner has no such duty)
In all cases, the occupant(s) of the home must be there legally, must not be fugitives from the law, must not be using the Castle Doctrine to aid or abet another person in being a fugitive from the law, and must not use deadly force upon an officer of the law or an officer of the peace while they are performing or attempting to perform their legal duties
Ref: Castle Doctrine in the United States - Wikipedia, the free encyclopedia