The title of the supreme judge was one of the powers of a monarch - first in the Kingdom of Poland and then in the Polish-Lithuanian Commonwealth. All judgements were rendered in the king's name, he had the power of pardon at his disposal and he was the last instance of appeal. The courts of the first instance in the Jagiellonian monarchy were land courts, magistrate courts and chamberlain courts. The fact that the court system was so complex already at such an early stage was a consequence of the adoption of the principle of inequality before the law - depending on the subject matter of the case, different types of court had to gather, in a relevant composition.
Rulings of courts of the first instance did not necessarily end the proceedings. When the defendant made use of appeal procedures, the case went before the second instance court: the rally court (which ceased to function in the fifteenth century) and the royal court. However, since the king was the final appellate instance, in a state as vast as Rzeczpospolita, it was impossible to conclude all cases. Despite this, discussions regarding the reform of the justice system continued for almost 40 years. On the one hand, king Sigismund Augustus defended his appellate prerogative over all his subjects, and on the other, noblemen were afraid of strengthening the role of the Senate, as those were the times of the executionist movement, which fought with determination to increase the importance of the nobility masses to detriment of the magnates, of whom the Senate was composed.
Finally, king Stephen Báthory was persuaded into a compromise. In 1578, the Polish law judiciary was separated from the monarch and the General Crown Tribunal was established. Similar institutions were established for Lithuania (1581), Prussia (1585) and Ukraine (1589-1590). The Tribunal consisted of judges, called deputies ['deputat'], who were elected once a year, in the number of twenty-seven, at deputies' assemblies. There were no considerable changes in the election of judges until the Constitution of 1764, which required from candidates to have legal expertise, to own land property for more than one year, not to be involved in proceedings and to have a clean criminal record.
Places for courts
In Great Poland of Piotrków, to which these Provinces shall belong: Poznańskie, Kaliskie, Sieradzkie, Ziemia Wieluń, Łęczyckie, Brzeskie, Inowrocławskie, Ziemia Dobrzyńska, Mazowieckie, Płockie, Rawskie.
In Lesser Poland of Lublin, to which these Provinces shall belong: Krakowskie, Sandomierskie, Ruskie, Podolskie, Lubelckie, Bełskie, Podlaskie, with the following proviso: those judges who have adjudicated the Provinces of Great Poland in Piotrków are to subsequently make way do Lublin and there adjudicate the Provinces of Lesser Poland for a period specified below. [...]
Prussian Provinces shall under our judges fall hence not the Tribunal but we ourselves shall adjudicate.
Lithuanian Kingdom Courts
The Grand Duchy of Lithuania shall adhere to its laws as established by the Union, the improvement of its statute as per the constitution of Lublin, 1569 and in congruence with the oath sworn by His Majesty Henryk and ours, in toto retaining, for the betterment of such judicial cases of the Grand Duchy of Lithuania, while designating the regional councils of Provinces to convene on the 23rd of May of the following year 1578. A greater congress is to be held on the Feast of the Archangels in Nowogródek for the States W.X.Lit. for the betterment of their laws, also this year. This betterment is to be brought fourth to the Sejm of the Commonwealth, for our confirmation. [...]
(Volumina Legum vol. II, St. Petersburg 1859, pp. 182-187)