The Assizes were a higher court, than for example the Petty Sessions, that could impose longer jail terms and even transportation or hanging. The courts were run by Judges who travelled around Ireland outside Dublin on 'circuits' with their clerks etc to the various towns for the Assize sessions.The judges were based in Dublin city and records for these session would been filed at the Four Courts complex - so unfortunately very little chance of any surviving.
There are some mentions of the Assizes in the Virtual Treasury which is is project to recover as much information as possible from the destruction of the Four Court & Public Records Office from damaged documents or alternate sources and copies from other repositories. I have not seen any complete court records or transcripts in these.
Several archives mention the Clonmel Gazette (e.g. National Library of Ireland, Tipperary Studies etc), it seem to only have covered 1788-1804.
There are some detailed reports from a case heard at the Clonmel Assizes in other newspapers - e.g. Clonmel Advertiser via Kilkenny Moderator 28th March 1818 (IrishNewsArchives) - the defendants mentioned are Burke, Cunningham and Ryan.
