> I think the idea is to test (with the jury as a sample) if the evidence is compelling enough for society at large to agree with the verdict.

Exactly. It's all about consent of the governed. We need the government to prove that they've got a valid reason to take someone's freedom before we let them do it. That's also why jury nullification is so important. It's another check on government to make sure that we feel that the laws we're being held to and the punishments we'll face when they are broken are acceptable.