The first Athenian law court was the Areopagus. It was introduced, according to tradition, when Demophon son of Theseus was king, and was competent to try serious crimes, such as premeditated killing (phonos ek pronoias). According to a second tradition, the name Areopagus arose from the trial of the god Ares, for the murder of Halirrothius son of Poseidon, and his acquittal. It was there that Orestes was brought to trial for the killing of his mother, and acquitted, the votes being equal, thanks to the casting vote of the god Athena. From that time on, if the votes in a case of killing were equal, this was considered as an acquittal for the accused. The Areopagus undoubtedly arose from the original council of elders, membership of which was a privilege of the nobles. In the Archaic period it was laid down that all should be members of it who had served as archons in the past.

To the period of the reign of Demophon, too, is attributed the formation of the body of the ephetai, though they are first mentioned in the laws of Dracon. There were fifty-one ephetai, but it is not clear if they were simultaneously members of the Areopagus or were a completely different body. Their competence included certain cases of killing not tried by the Areopagus. Depending on circumstances they would meet in a different place. For trials of involuntary killing, attempted killing, and killing of a metic, foreigner, or slave, they would meet in the Palladium at Phalerum. In cases where the doer of the deed maintained that it had been a just killing (dikaios phonos), they would meet in the temple of Apollo Delphinius. Anyone who, while already in exile for some other killing, faced a new charge of killing, was tried at Phreattys. The ephetai would stand on the shore and the accused in a boat, so as not to pollute the city. Lastly, cases against inanimate objects that had caused somebody's death, or cases where in general the doer of the deed was unknown, were tried in the Prytaneum. The trying of cases of this kind was within the competence not of the ephetai but of the prytaneis (Aristotle, Athenaion Politeia 57.3-4).

At the same time the post of thesmothetes was created. The institution was in antiquity a more general category than the law and was not necessarily framed in a definitive (written) form. The strength of institutions stemmed from the belief that there were very ancient inviolable canons, bound up with the first societies ever created from permanently settled farmers. Their violation entailed anything from simple curses (arai) to exclusion and banishment from society, with simultaneous confiscation of property (atimia). These sacred institutions were attributed to Demeter Thesmophorus. Their maintenance was overseen by the thesmothetes, who were six in Archaic Athens. They also took care of their codification, and also of the writing down and publishing of the verdicts, to make future judgments easier. From the end of the 7th century B.C., the powers of the thesmothetes were extended and they themselves flanked the archon basileus, the polemarch, and the eponymous archon, all of them collectively comprising the Nine archons (Pollux, Onomasticon 8.85-86). Cleisthenes added a secretary, so that the number of archons should correspond to the number of new tribes. After Cleisthenes, it was the thesmothetes who filed private and public lawsuits (dikai, graphai) connected with security and order in the city, but their powers were now more nominal, and less substantial.

At the start of the 6th century, one of the reforms put into practice by Solon was the formation of the Eliaia, the first People's Court. All citizens over the age of thirty could attend this if they showed their willingness to take part by having their names recorded on the relevant tablets. They were chosen by lot, and a special machinery, the cleroterium, was used for this purpose. In the Classical period it was to the Eliaia - which at that time was, in some scholars' view, simply a juridical accompaniment of the Assembly of the demos - that competence passed for trying all crimes that had previously been referred to the Areopagus and the archons.

The Council of Five Hundred founded by Cleisthenes also had certain judicial powers in cases of wounding with intent to inflict death (traumata ek pronoias). To the Council, too, belonged control of all Athenian archons, the only exception being the generals, who were exclusively controlled by the Eliaia.

Also with juridical competence in certain cases was a body with policing duties, the Eleven. The Eleven were appointed by lot. Besides overseeing the prison, its prisoners, and the carrying out of death sentences, they could try certain criminals caught in the act. Such cases were those of thieves, slave traders attempting to sell free men as slaves (andrapodistai), 'rififi men' (toichorychoi), and 'cutpurses' (balantiotomoi). The Eleven exercised their judicial rights in two ways: either di' apagoges (by citizen arrest) or di' ephegeseos (by laying an information). In the first case, they haled the accused, the man caught in the act, before them; in the second they themselves went to the scene of the crime and arrested him (Aristotle, Athenaion Politeia 52.1).

Besides the city's law courts and juridical institutions, there were also local jurymen for the resolution of minor differences, in the demes or tribes. Pisistratus introduced the law court of the Forty. Here the jurymen were from all the tribes but were chosen by lot to judge cases in tribes other than their own: this at least is what Demosthenes says about the Oineis and the Erechthieis. Lastly, there were the diaitetai, including in theory all Athenians over the age of sixty.