The trial of Crown cases normally occupied one judge for the duration of each assize. Under the terms of the oyer and terminer and gaol delivery commissions assize judges were empowered to determine felonies, misdemeanours, and treasons and to try all suspects bailed or held in gaol within the counties of their circuits. Their association with the delivery of suspect felons detained in local gaols was of course by no means new. From at least as early as 1330 assize judges, in the ‘modern’ sense of Serjeants or justices of the central courts travelling regular circuits, were employed consistently in this work. That they failed for a further three centuries to secure a monopoly of provincial gaol delivery was the result of two principal factors. The first was the continued existence of franchise jurisdictions enjoying special arrangements for the delivery and trial of suspects. Most of these exceptions had been assimilated into the national system by the mid-seventeenth century, but at least one criminal franchise–the Bishop of Ely's liberty in the Isle–remained intact into the nineteenth century.