Sejm court
A sejm court was a court that sat in cases of impeachment--in the words of the May 3rd Constitution of 1791 (article VIII: the judicial authority)--of government "ministers [...] charged with breach of law by a deputation designated to examine their deeds [...]."
The composition and functioning of sejm courts were spelled out in a special act of the Sejm passed on May 13, 1791.