Malfeasance in office, or official misconduct, is the commission of an unlawful act, done in an official capacity, which affects the performance of official duties. Malfeasance in office is often grounds for a for cause removal of an elected official by statute or recall election.
An exact definition of malfeasance (or misfeasance (Brit)) in office is difficult: many highly regarded secondary sources (such as books and commentaries) compete over its established elements based on reported cases. This confusion has arisen from the courts where no single consensus definition has arisen from the relatively few reported appeal-level cases involving malfeasance in office.
The West Virginia Supreme Court of Appeals summarized a number of the definitions of malfeasance in office applied by various appellate courts in the United States.
The court then went on to use yet another definition, "malfeasance is the doing of an act which an officer had no legal right to do at all and that when an officer, through ignorance, inattention, or malice, does that which they have no legal right to do at all, or acts without any authority whatsoever, or exceeds, ignores, or abuses their powers, they are guilty of malfeasance."
Nevertheless, a few "elements" can be distilled from those cases. First, malfeasance in office requires an affirmative act or omission. Second, the act must have been done in an official capacity—under the color of office. Finally, that that act somehow interferes with the performance of official duties—though some debate remains about "whose official" duties.
In addition, jurisdictions differ greatly over whether intent or knowledge is necessary. As noted above, many courts will find malfeasance in office where there is "ignorance, inattention, or malice", which implies no intent or knowledge is required.