Two senior judicial officers of the Isle of Man, historically central to the Island’s courts, legislature and declaration of customary law.

The office is documented in medieval Manx law. A declaration made at Castle Rushen in 1422 records the Deemsters acting with the Twenty-four Keys to state the law of the Island. Later constitutional descriptions continued to place two Deemsters within the machinery of government.

A seventeenth-century account described them simply as “two Deemsters or Judges” chosen by the Lord and identified them as judges of the Common Law. By the eighteenth century their jurisdiction extended across both civil and criminal business. The 1792 constitutional inquiry recorded the Deemsters among the senior officers who attended the Governor and Council and repeatedly referred to their judicial role in the Common Law Courts, the sheading system and the administration of oaths.

The office was particularly associated with the declaration of Manx customary law. Nineteenth-century writers described the older body of unwritten custom as “Breast Law”, preserved and pronounced by the Deemsters before increasing amounts of Manx law were committed to writing.

The Deemsters also participated in Tynwald. Their exact historical right to a fixed seat in the Council was disputed in evidence given to the 1792 Commissioners, but the Attorney-General acknowledged that they appeared never to have been absent from meetings of the legislature.

Their judicial authority was not merely advisory. Contemporary descriptions state that they heard and determined causes, administered the law in the Common Law Courts and acted in proceedings concerning both land and personal property.