There are three main types of adverse interests.
1) An adverse interest can mean an interest, claim or right that is against another’s interest. For example, a plaintiff and defendant have adverse interests.
2) A witness with adverse interest means the witness is hostile. A hostile witness wants different results of the lawsuit than the party who calls him. Rule 611 at Federal Rules of Evidence allows a party to ask a witness with adverse interests leading questions even in direct examination in a trial.
3) In real property, adverse interest means a person, who’s not the owner of the land or house, owns an interest of this property. For example, a neighbor A owns an easement, which gives A the right to pass B’s land to access public road, on the land of owner B. In this case, A has an adverse interest on B’s land.
[Last updated in May of 2020 by the Wex Definitions Team]