A iudicium populi (literally "popular trial" or "popular judgement"; also called a iudicium publicum in earlier periods) was a judicial trial, primarily in the Roman Republic, before one of the popular assemblies. In the proceedings the popular assembly and the people that made it up heard evidence from the prosecuting magistrate and the defendant before rendered a final verdict directly. The presiding and prosecuting magistrate were most often aediles or plebeian tribunes but more rarely could also be one of the quaestors, the duumviri perduellionis, or in religious cases the pontifex maximus.
In the early republic these popular trials were believed to be the only means by which large fines or capital punishments could be administered at Rome, since the Twelve Tables and the laws permitting a citizen's appeal to the people and tribunes (provocatio and auxilium, respectively) made it illegal for a magistrate to otherwise punish a citizen. However, by the second century BC they competed for jurisdiction with the quaestiones perpetuae (permanent jury courts) which heard cases on specific types of cases (such as corruption, public violence, and murder) in a more streamlined manner. The emperors' arrogation of provocatio and assertion of exclusive jurisdiction over the criminal law by the early empire made the iudicium populi obsolete.
