A special master or master in chancery is an individual appointed by the court to assist with some part of a lawsuit, such as discovery—depositions, written questions, and production of documents—and to make recommendations to the judge on how to resolve related disputes. Courts have held that discovery questions that require extensive examination of highly technical and complex documents by a person having both a technical and a legal background may constitute an exceptional condition sufficient to justify the appointment of a master to supervise such discovery.

In California, a special master, sometimes referred to as a master in chancery, is an expert appointed by the court to assist in specific aspects of a legal case, particularly when the matter involves complex and technical issues that require specialized knowledge. The role of the special master is to oversee certain procedures, such as discovery, which includes managing depositions, interrogatories, and the production of documents. They also provide recommendations to the judge on how to resolve disputes related to these procedures. The appointment of a special master is generally considered an exceptional measure, reserved for cases where the discovery process involves the examination of highly technical and complex documents that necessitate expertise in both technical and legal fields. California courts may appoint a special master under California Rules of Court, Rule 3.920 through 3.923, when they determine that the circumstances of the case warrant such an appointment to ensure efficient and effective management of the litigation process.