This is why you are tried by twelve jurors, not one or three. You'd have to be extremely unlucky to have ten out of twelve such idiots on your jury. Fewer means, at worst, a mis-trial. More likely, one good (wo)man and true on your jury will denounce the idiot(s) to the judge as soon as (s)he becomes aware of them.
There's a case to be made for ensuring that a minority of a jury are technically competent (for example, accountants in fraud trials; scientists where forensic evidence is complex). Maybe 4/12 of them. Never a majority, let alone all. Selecting such a group is likely to select for correlated prejudice.