"Self-defense" of self, others or property, is an example of an affirmative defense. The right to self-defense is a basic human right that has been recognized from ancient times, and recognized in the laws on self-defense.
"The right of self defense never ceases. It is among the most sacred, and alike necessary to nations and to individuals."
Johnny Apple drives to the store to buy some items. In the parking lot, a man he does not know begins to yell at him about money he supposedly owes the man. Then the man proceeds to brutally assault Johnny, during which Johnny notices he is attempting to pull out a knife. Fearing for his life, Johnny breaks the man's neck which kills him. The government charges (makes the claim of) criminal murder. At the trial, Johnny's Minnesota defense lawyer questions witnesses who testify about what they saw and heard of the brief assault. The jury was convinced that it was not a murder to prevent collection of a debt, but a killing in self-defense because the "force" used by Johnny was "reasonable" under the circumstances of the attempted robbery. "Not guilty."
President James Monroe
Minnesota's self-defense law contains a "duty to retreat" provision. A person facing a threat has a duty to retreat where practical, before responding with "reasonable force." If an attack is sudden retreat might be unrealistic or create a risk of bodily harm. In order to protect you, your loved ones, or your property, in some situations there may be no reasonable alternative to the use of reasoanble force in self-defense.
What is "reasonable force?" There must be thousands of court cases discussing this, in various situations. The idea is that the level of force used in self-defense should be commensurate with the perceived threat level at the time.
Police are trained to shoot the center of the body when shooting in self-defense, and to shoot a person armed with a knife within striking distance. That could be reasonable force. No one wants to end up in a case where a jury has to decide "was it reasonable?" given the threat presented at the time. If you are defending yourself or others from a violent attack, however, even deadly force can be reasonable.
"Here one must be clear that there are three different views on the subject of violence. One is the approach of pure nonviolence, which cannot readily or easily attract large masses, for it requires extraordinary discipline and courage. The second is violence exercised in self-defense, which all societies, from the most primitive to the most cultured and civilized, accept as moral and legal. The principle of self-defense, even involving weapons and bloodshed, has never been condemned, even by Gandhi, who sanctioned it for those unable to master pure nonviolence. The third is the advocacy of violence as a tool of advancement, organized as in warfare, deliberately and consciously. ...
There is more power in socially organized masses on the march than there is in guns in the hands of a few desperate men. Our enemies would prefer to deal with a small armed group rather than with a huge, unarmed but resolute mass of people. However, it is necessary that the mass-action method be persistent and unyielding."
Serving The People of the local Mpls - St PaulTwin Cities metropolitan area in Hennepin County, Ramsey County, Anoka, Sherburne, Wright, Carver, Scott, Dakota, and Washington Counties (greater Minnesota only upon special consideration).