Private citizens may use deadly force in certain circumstances in self-defense. The rules governing the use of deadly force for police officers are different from those for citizens.
In most jurisdictions, the use of deadly force is justified only under conditions of extreme necessity as a last resort, when all lesser means have failed or cannot reasonably be employed. Firearms, bladed weapons, explosives, and vehicles are among those weapons the use of which is considered deadly force. The use of non-weapons in an aggressive manner, such as a baseball bat or tire iron, may also be considered deadly force.
In the United Sates, a citizen may legally use deadly force when it is considered when the civilian feels their own life, or the lives of their family or those around them are in legitimate and imminent danger. Self-defense resulting in usage of deadly force by a civilian an individual or individuals is often subject to examination by a court if it is unclear whether it was necessary at the point of the offense, and whether any further action on the part of the law needs to be taken.
There are specific laws, state to state but this standard is fairly uniform across the United States. This standard has its roots in common law and has been used as a benchmark in law enforcement training.
You will have to do a little research on your particular State’s laws pertaining to Deadly Force as I have been unable to find one reliable link that offers information on all States. It is easy to find them though on an individual state search. With the constant changes, I am not able to place them all here individually.
Generally, three elements that must be present are called Ability, Opportunity, and Jeopardy. When these three things are present, any reasonable person would believe that a life was in danger, therefore making the the defendant’s legal position very strong. Having any of these elements missing, makes it more difficult to prove to a jury that the use of deadly force was necessary.
Ability means that the other person has the power to kill or to cripple you. Opportunity means that the circumstances are such that the other person would be able to use his ability against you. Jeopardy means that the other person’s actions or words provide you with a reasonably-perceived belief that he intends to kill you or cripple you.
Here is a great article written by lethal force expert Massad Ayoob regarding the use of deadly force in a rape. http://www.backwoodshome.com/articles/ayoob65.html
A Castle Doctrine (also known as a Castle Law or a Defense of Habitation Law) designates one’s place of residence (or, in some states, any place legally occupied, such as one’s car or place of work) as a place in which one enjoys protection from illegal trespassing and violent attack. It then goes on to give a person the legal right to use deadly force to defend their place, and any other innocent persons legally inside it, from violent attack or an intrusion which may lead to violent attack. In a legal context, therefore, use of deadly force which actually results in death may be defended as justifiable homicide under the Castle Doctrine.
Castle Doctrines are legislated by state though not all states in the US have a Castle Doctrine law.
Each state has its own Castle laws, which have a number of limitations and exclusions to the law. Generally speaking, though,
and you MAY:
In all cases, the occupant must legally be in the residence, and the intruder must be there illegally. Additionally, Castle laws may extend these rights to a workplace, car, or other residence where the occupant is legally.
In some states, the Castle Doctrine provides complete immunity, including from future civil suits brought forth by the intruder and/or the intruder’s family.