For centuries, the law has recognized a person’s right to use deadly force to defend against an intruder who unlawfully and forcibly enters a person’s home. This common law principle—known as the castle doctrine—was generally recognized by judges and criminal prosecutors for hundreds of years, and has more recently been included in statutes enacted by many state legislatures. These statutory self-defense protections sometimes extend beyond the victim’s home and apply in other physical locations, such as occupied motor vehicles and places of employment.

For example, in 2005 Florida passed a law that expanded on the castle doctrine and included language stating that if a person is in any location he or she has a right to be—and is not engaged in an unlawful activity—the person has no duty to retreat from an attacker and has the right to stand his or her ground, meeting force with force (including deadly force) if he or she reasonably believes such force is necessary to prevent his or her own death or great bodily injury, or the death or great bodily injury of another—or to prevent the commission of a forcible felony offense. Some states include the threat of certain types of kidnappings (usually by non-family members) and the threat of sexual intercourse compelled by force or threat as justifying deadly force in self-defense.

Today, laws in at least 25 states provide that there is no duty to retreat from an attacker in any place in which the victim is lawfully present. These states include: Alabama, Alaska, Arizona, Florida, Georgia, Idaho, Indiana, Kansas, Kentucky, Louisiana, Michigan, Mississippi, Missouri, Montana, Nevada, New Hampshire, North Carolina, Oklahoma, Pennsylvania, South Carolina, South Dakota, Tennessee, Texas, Utah, and West Virginia. And at least ten of these states include language that such a victim may “stand his or her ground”—including Alabama, Florida, Georgia, Idaho, Kansas, Kentucky, Louisiana, Oklahoma, Pennsylvania, and South Carolina.

Some states distinguish between a victim’s use of deadly force in the victim’s home, vehicle, or place of work—which is presumed to be reasonable to prevent death or serious bodily injury—and the use of deadly force in other locations, where a victim may have a duty to retreat before using deadly force, if the retreat can be made safely.

In addition to these statutes that provide defenses to criminal prosecutions when a victim uses force (including deadly force) in self-defense, some state statutes address the related issue of civil liability in a civil lawsuit that may be filed by a person against whom such force is used. Self-defense laws in at least 23 states provide such civil immunity under certain self-defense circumstances.

Self-defense and stand your ground laws are generally located in a state’s statutes, and usually in the penal or criminal code.

In Maine, the right to use deadly force in self-defense is recognized under the state's statutes, particularly when an individual is defending themselves within their own home. This principle is rooted in the common law concept known as the 'castle doctrine,' which allows individuals to use reasonable force, including deadly force, to protect themselves against an intruder. Maine law does not specifically have a 'stand your ground' law that removes the duty to retreat in any place where an individual is lawfully present, unlike some other states. Instead, Maine law generally requires a person to retreat if it is safe to do so before using deadly force in self-defense, except when the person is in their own dwelling. Additionally, Maine's statutes provide for the use of deadly force in self-defense not only to prevent death or great bodily injury but also to prevent certain serious crimes. Regarding civil liability, if the use of force is justified under Maine's self-defense laws, the individual may also have immunity from civil lawsuits brought by the person against whom the force was used.