From United Press International:
In America we like our juries dumb and predictable. God forbid they should know anything about the case they're judging, much less the law they're judging it by. We need to protect them from all sorts of things that could infect their brains with information.
If we didn't do that, it would be like trusting 12 guys off the street to dispense justice. What a quaint idea. And, obviously, a dangerous one.
The idea of a jury is at least 3,000 years old -- the Greeks thought 12 was the perfect number of panelists -- but our version of it is much younger. We're coming up on the 800th anniversary of the year when King John was told, essentially, stop forcing your laws down our throats or we're going to burn down your castle.
Voila! The modern jury system was born. The king could decree all the laws he wanted to decree, but from then on it would be 12 guys from the neighborhood who decided whether they would actually be used against anybody.
More here.