A judge may be disqualified from hearing or presiding over a matter in which provable facts suggest the judge has a disqualifying conflict of interest. The related legal process of recusal of a judge is generally based on the perception of impartiality due to circumstances that suggest a conflict of interest—but not to the same degree as the facts that establish disqualification.

The standards for disqualification of a judge vary from state to state, and disqualification is rare. But a judge is generally disqualified in any proceeding in which:

(1) the judge has served as a lawyer in the matter in controversy, or a lawyer with whom the judge previously practiced law served during such association as a lawyer concerning the matter;

(2) the judge knows that, individually or as a fiduciary, the judge has an interest in the subject matter in controversy; or

(3) either of the parties may be related to the judge by affinity or consanguinity within the third degree.

In California, a judge may be disqualified from presiding over a case if there are provable facts that suggest a conflict of interest. This is governed by the California Code of Civil Procedure Section 170.1, which outlines specific circumstances under which a judge must be disqualified. These include having previously served as a lawyer in the matter, having a personal or fiduciary interest in the subject matter, or being related to a party within the third degree of consanguinity or affinity. Additionally, California law allows for a peremptory challenge of a judge under Section 170.6, where a party can request a different judge without proving bias, but this must be done in a timely manner and is subject to certain limitations. The process of recusal, where a judge voluntarily steps down from a case due to potential bias or conflict of interest, is also recognized, although it is less formal than disqualification and is based on the judge's assessment of their ability to remain impartial.