In common law, a next friend (Law French prochein ami) is a person who represents another person who is under disability or otherwise unable to maintain a suit on his or her own behalf and who does not have a legal guardian. In England and Wales they are known as litigation friends. When a relative who is next of kin acts as a next friend for a person, that person is sometimes instead described as the natural guardian of the person. A next friend has full power over the proceedings in the action as if he or she were an ordinary plaintiff, until a guardian or guardian ad litem is appointed in the case; but the next friend is entitled to present evidence only on the same basis as any other witness.
This disability often arises from minority, mental incapacity, or lack of access to counsel. Consequently every application to the court on behalf of a minor, a mentally incapacitated person, or a person detained without access to an attorney, who does not have a legal guardian or someone authorized to act on his or her behalf with a power of attorney, must be made through a next friend (prochein ami, prochein amy, or proximus amicus). A minor frequently defends a suit not by a next friend but by a guardian ad litem, often appointed by the court with jurisdiction over the case or by a court with probate jurisdiction.
Before the Married Women's Property Act 1882 in British law (and similar acts during the same period in American law), it was usual for a married woman to sue by a next friend; but that act, allowing a married woman to sue in all respects as a feme sole, has rendered a next friend unnecessary in the case of married women.
Historically, in the case of a minor, the father is prima facie the proper person to act as next friend; in the father's absence, the testamentary guardian, if any, is next friend; but any person not under disability may act as next friend so long as he has no interest in the action adverse to that of the minor. A married woman could not historically act as next friend; but this practice is no longer current, at least in the United States.
In the case of mental incapacity, a conservator, guardian, or committee represents the person in court, but if they have no such representative, or if the committee has some interest adverse to the claimant, they may sue by a next friend.