Re: Why is a jury tainted if they have heard about a case through the press?
The ancient presumption was to find a jury of people who were familiar with the facts, not people who knew none of them. We have switched that idea around, obviously.
One of the reasons for avoiding "tainting" is to make sure a jury is not exposed to evidence that a judge decides is too flawed to be presented, like a forced confession. The general idea is to have the jury's picture of the case formed by the trial process, not the media.
Mark Twain agreed with you though.