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Capacity refers to the ability to make a rational decision based upon all relevant facts and considerations. Some common usages of the term “capacity” in a legal sense include: 

  • In the context of criminal law, the term “capacity” means that the defendant must have the ability to understand the wrongfulness of their actions.
  • In the context of contract law,  the term “capacity” denotes a person's ability to satisfy the elements required for someone to enter binding contracts.  For example, capacity rules often require a person to have reached a minimum age and to be of sound mind. A contract signed by a person lacking capacity may be void or voidable
  • In the context of wills, the maker of a will must have testamentary capacity. Cases such as this one from the D.C. Court of Appeals, explain that “’testamentary capacity’ is the mental state that a person must possess at the time of making a will in order for the will to be valid.”

[Last updated in March of 2022 by the Wex Definitions Team]