Sanhedrin 4 - Written or Pronounced Torah Words
The real reason why Rabbi Yehudah the Prince requires five judges is because in "... whomever the judges condemn ..." the word "condemn," ירשיען is plural, which means two judges. Another two judges are mentioned below, and since the court needs an odd number of judges to be able to rule by majority, the total is five.
The Sages, however, say that since the word "condemn" ירשיען is written defectively, without an usual letter vav ירשיעון that one would expect for plural, it means one judge. Therefore, their count is three judges.
The basic argument here is whether the pronounced form of the word (Rabbi Yehudah) or its written form (Sages) is more important. Other arguments hinging on the same "written or pronounced" premise include the number of blood applications of a sacrifice needed for atonement, the number of walls in a sukkah, and the amount of blood from two corpses that creates ritual impurity.
Art: Jean Changenet - Three Prophets