Justiciar’s Courts
Origins
Initially, the justiciar was both the chief judge and governor. There was no clear-cut division between the judicial, administrative or government functions.
The Irish justiciar’s court corresponded to that of the English court coram rege. Claims based on errors in the lower courts could be referred to the justiciar’s court. The court usually exercised its functions in Dublin.
The justicar was not necessarily legally trained.There was accordingly a justice attached to the court. The justice was on some occasions allowed to deal with minor business. He could hear cases with the consent of the parties sitting alone.
Separation of Judicial Functions
From the latter part of the 13th century, the justiciar had a judicial assistant, known as the justice of the justiciar. From the 1280s he had a professionally qualified judge assisting him. From the middle of the fourteenth century, a second justice was appointed who was termed Chief Justice of the pleas following the Justiciar. From then onwards the court was orientated more towards the justice than the Justiciar / Lord Deputy.
Initially the Justiciar was present in person. Sometimes between appointments while the Justiciar was not present, his place would be taken by an official custos who had powers. He might adjourn  the case to the Justiciar.
When the King came to Ireland at the end of the 14th century, the  Justiciars’ powers were suspended. Ultimately the Justiciar did not subsequently sit in the court and the court was thereafter presided over by professional judges. The court retained the name of Kings Bench as it technically had been during the period in which Richard II had stayed in Ireland. Ultimately in the 16th century, the King’s Bench Court became permanent in Dublin.
Jurisdiction
The Justiciars court was itinerant in this period and was the equivalent of the King’s Bench in Ireland to which there was in practice little recourse. It was based in Dublin but  travelled through the country.
In 1207 the King granted to all men in Ireland that should not answer for anything or in any court respecting free tenement save by the King’s order or writ or those of his Justiciar nor touching any plea of the crown save before the King, his Justiciar or the justice whom the King or the Justiciar sent to administer the law.
Accordingly, cases relating to freehold might be heard in seniororial courts, but must be begun by a writ from the king or Justiciar. Pleas of the crown must come before the Kings court, i.e. the King’s Bench in England, which is the Justiciar’s court, or the court of the itinerant justices.
Criminal Busines
At the beginning of the 13th century, the justiciar exercised jurisdiction in both civil and criminal matters.The criminal business in the justiciar’s court was entered under separate rolls or files. At the full county sessions, the sheriff and coroners with the roles and inquisitions were present.
Offences which might be heard included homicide, rape, robbery, offences against property, arson. Fines mainprises and amercements were imposed.
Hanging was not as common as later was the case.  Fines and outlawry were possible Pardons were given from time to time for service to king. The benefit of the clergy might be claimed by persons in religious orders.
The juries were generally of up to 12 persons. They deal both with criminal and administrative business. Juries of presentment dealt with quasi-governmental matter. Petty juries were involved in judicial matters.