Reasonable Force Law and Legal Definition

Reasonable force refers to the amount of force necessary to protect oneself or one's property. Reasonable force is used to defend one's person or property from a violent attack, theft, or other type of unlawful aggression. It is used as a defense in a criminal trial or to defend oneself in a suit alleging tortuous conduct. When a person uses excessive force or more than the force necessary for such protection, s/he is considered to have forfeited the right to defense.

In the case of a trespass, the lawful occupant of a property must request the trespasser to leave the property. When the trespasser does not leave within a reasonable time and it would appear to a reasonable person that the trespasser poses a threat to the property, then the owner/occupants can use reasonable force to make the trespasser leave. Reasonable force in this case means the amount of force that a reasonable person in the same situation would believe is necessary to make the trespasser leave. When the trespasser resists, the lawful occupant can increase the amount of force in proportion to the force used by the trespasser and the threat the trespasser poses to the property. In determining whether the defendant used reasonable force, the court must consider all the circumstances as they were known to and appeared to the defendant and consider what a reasonable person in a similar situation with similar knowledge would have believed. When the defendant's beliefs were reasonable, the danger does not need to have actually existed. The People have the burden of proving beyond a reasonable doubt that the defendant used more force than was reasonable. When the People do not meet this burden, the defendant is not guilty. [People v. Johnson, 180 Cal. App. 4th 702, 708 (Cal. Ct. App. 2009)]

In the context of an arrest, reasonable force means "such force as is necessary under the circumstances to effectuate the arrest”. [Faust v. Clee, 2006 U.S. Dist. LEXIS 76770 (D. Pa. 2006)]