In order to prevent the courts from being clogged with cases completely lacking merit, a kind of nuisance fee of a thousand drachma was assessed against those who brought charges but failed to get at least 20% of the vote from the jury. For Socrates' trial this meant that Meletus, Anytus, and Lycon had to obtain at least 101 votes from the jury of 501.
Since a drachma was the equivalent of a day's wage, a payment of a thousand
drachma was a hefty fine indeed. Prosecutors had to be sure of their
claims before making formal charges.