Law Enforcement in Ancient Greece
Foreign slaves were often employed to police the cities of ancient Greece. Greeks found it uncomfortable to have citizens policing their own fellow citizens. Often Greeks relied on citizens to report crimes. After reporting a crime, if an arrest was made, an informant would receive half of the fine charged to the criminal.
In Athens, criminals were tried before a jury of 200 or more citizens picked at random. Criminals were punished by fines, their right to vote taken away, exile, or death. Imprisonment was not typically used as a punishment.