That is really interesting the differences there. I think the intended goal of the US system is to make sure that you get 12 people capable of being objective about the subject at hand, rather than 12 random people. For example, it usually takes all 12 jurors to make a conviction, so if you get just one person who won't convict no matter what because of religious reasons or pre-existing biases or whatever, then automatically you have a hung jury that can't be swayed by evidence. So the US system tries to insure we get 12 people who are willing to put aside their biases and be objective (enough) to render a verdict based on the facts before them either way the facts lead. So it's a long process, but in our system anyway we try to weed out anybody who might believe, for example, that all Mexicans are criminals if it's a Mexican on trial, or someone who doesn't believe that rape should be a crime in a rape case. And the big one of course, people who are already so convinced by media they've consumed that the person is guilty that they can't act as a fair juror.