Latin; literally "hear the other side".
The maxim means, in law, that no person shall be condemned, punished or have any property right deprived, unheard.
A principle of natural justice which prohibits a judicial decision which impacts upon individual rights without giving all parties in the dispute a right to be heard.
Habeas corpus was an early expression of the audi alteram partem principle.
In more recent years, it has been extended to include the right to receive notice of a hearing and to be given an opportunity to be represented or heard at that hearing.
The expression received this endorsement from the US Supreme Court (1958, Caritativo v. People of State of California 357 US 549):
"Audi alteram partem - hear the other side! - a demand made insistently through the centuries, is now a command, spoken with the voice of the due process clause of the 14th Amendment, against state governments, and every branch of them - executive, legislative, and judicial - whenever any individual, however lowly and unfortunate, asserts a legal claim.
"It is beside the point that the claim may turn out not to be meritorious. It is beside the point that delay in the enforcement of the law may be entailed ...
"The right to be heard somehow by someone before a claim is denied, particularly if life hangs in the balance, is far greater in importance to society, in the light of the said history of its denial, than inconvenience in the execution of the law. If this is true when mere property interests are at stake ... how much more so when the difference is between life and death?"