After the speeches and other evidence had been presented, the members of the jury voted by casting ballots. A series of vase paintings of the early 5th century B.C. show a mythological story, the vote for the arms of Achilles. In these scenes the Greek heroes vote using pebbles, observed by many bystanders, suggesting that the concept of a secret ballot did not yet exist. Whether or not the voting scenes that appear on vases depicting this story show an actual method of voting in early 5th-century Athens, their appearance at this time may have been prompted by the enhanced importance of voting that resulted from the reforms of Kleisthenes.
The voting scene in Aeschylos' play Eumenides, produced in 458 B.C., suggests that by this time a means of voting secretly existed. We are told that in voting on whether Orestes should live or die, the contesting parties placed their ballots (pebbles or mussel shells) into one of two urns, one for the prosecutor, the other for the defendant. Although it is hard to see how this procedure could be secret, since the choice of urn might be observed by anyone present, it seems that the Athenians had devised a way to maintain secrecy, for in the vote over Orestes' fate, the outcome is in doubt until the votes are counted. Athena, casting her vote in Orestes' favor, says:
If the other votes are even, then Orestes wins.
You of the jurymen who have this duty assigned,
Shake out the ballots from the vessels, with all speed.
(Aeschylos, Eumenides 740-743, translated by Richard Lattimore)
By the mid-4th century B.C. the system had changed to that described by Aristotle:
There are bronze ballots, with an axle through the middle, half of them hollow and half solid. When the speeches have been made, the men appointed by lot to take charge of the ballots give each juror two ballots, one hollow and one solid, in full view of the litigants so that no one shall take two solid or two hollow... There are two jars in the court, one of bronze and one of wood.... The jurors cast their votes in these: the bronze jar counts and wooden does not; the bronze one has a pierced attachment through which only one ballot can pass, so that one man cannot cast two votes. When the jurors are ready to vote, the herald first makes a proclamation, to ask whether the litigants object to the testimonies: objections are not allowed once the voting has begun. Then he makes another proclamation: 'The hollow ballot is for the litigant who spoke first (prosecutor), the solid for the one who spoke afterwards (defendant)' The juror takes his ballots together from the stand, gripping the axle of the ballot and not showing the contestants which is the hollow and which is the solid, and drops the one that is to count into the bronze jar and the one that is not into the wooden. (Athenian Constitution 68, translated by P.J. Rhodes)
If the vote was for guilty, then there was a second phase of the trial to set the penalty. After additional speeches, the jury then decided between two punishments, one proposed by the prosecution, the other by the defense. If the prosecutor failed to get a sufficient number of guilty votesat least one fifth-his case was deemed unworthy, and he himself was fined.
Some forty-eight ballots fitting Aristotle's description have been found in the Agora, some actually inscribed "official ballot." A ballot box has also been identified.