We can understand many of the differences if we keep in mind that the Greeks thought that the courts should be just as democratic as the rest of their government . The Athenians put together huge pools of jurors, the larger juries for the more serious crimes. Large juries are good for at least two reasons. The Athenians wanted to keep justice in the hands of the people, and so rejected any significant role for legal professionals. Finally, there were no professional judges .
Courts have to decide at least three different sorts of issues.
They were sceptical of written documents, as they worried about forgeries. Witnesses counted for a bit more, but they too could lie. The most important part of the trial, then, were the speeches given by the defendant and the prosecutor. It's a little like skipping everything else and going straight to the closing argument. And it was just as important for you to show that you had a good character as to make the winning arguments.