http://agathe.gr/democracy/the_verdict.html
The Verdict 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, ... 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.