In pre-independence Ireland, a Resident Magistrate was a stipendary magistrate appointed to a county (outside of the Dublin Metropolitan Police District) to sit among the justices of the peace at Petty Sessions in that county. They were appointed by the Lord Lieutenant of Ireland (in reality, therefore, by the Dublin Castle administration in Ireland). The Petty Sessions in the early 19th century replaced the Manor Courts which were inefficient and often corrupt.
Petty sessions were originally held by justices of the peace, who were lay people (and in Ireland, typically members of the Protestant Ascendancy and as the 19th century advanced local eminent citizens), as preliminary hearings for Quarter Sessions and the assizes). From 1836, the justices acted under the supervision of resident magistrates. The Petty Sessions (Ireland) Act 1851 regulated petty sessions, organising the country into petty sessions districts and providing for the appointment of clerks of petty sessions. A series of Summary Jurisdiction (Ireland) Acts, beginning in 1851, vested petty sessions with summary jurisdiction in minor criminal matters. Both these Acts are still on the statute book, though heavily amended. In Dublin, the divisional magistrates exercised similar power to petty sessions under the Dublin Police Acts.
In practice the Clerk of Petty Sessions held considerable sway having a knowledge of law even if rudimentary and procedure.