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 Missouri, a special master, also known as a master in chancery, can be appointed by the court to assist with complex aspects of a lawsuit, particularly during the discovery phase. This appointment is typically made under exceptional conditions where the case involves highly technical or complex documents that require the expertise of someone with both technical knowledge and a legal background. Missouri courts follow Rule 53 of the Missouri Rules of Civil Procedure, which outlines the appointment, powers, duties, and compensation of a special master. The rule allows for a special master to be appointed when the issues are complicated and it would be impractical for the court to address them without assistance. The special master's role includes gathering evidence, conducting hearings, and making recommendations to the judge on how to resolve discovery-related disputes. The judge is not bound by the master's findings and recommendations but gives them due consideration. The use of a special master is intended to streamline the legal process and provide specialized expertise in cases where it is deemed necessary.