In legal procedure (both civil and criminal), misjoinder refers to a wrongful joinder.
Misjoinder of causes of action, or counts, consists in joining several demands to enforce substantive rights of recovery that are distinct and contradictory.
Misjoinder of parties consists in joining as plaintiffs or defendants persons who have conflicting interests, or who were not involved in the same transaction or event.
United States
According to FRCP Rule 21,
Misjoinder of parties is not a ground for dismissing an action. On motion or on its own, the court may at any time, on just terms, add or drop a party. The court may also sever any claim against a party.
References
Misjoinder Wikipedia(Text) CC BY-SA