1) Yes: We do expect the jury to base their decisions solely on the information they are given *IN RELATION TO THE CURRENT CASE*. Unless there is evidence to support a link to a previous case, and said link is accepted by the Judge, then previous convictions and certainly accusations are irrelevant.
2) The Internet and the media are full of lies, half-truths, opinions and deceptions. You don't have to look far in the news to see examples of this, and unless you research those stories carefully, you'll be led to the wrong conclusion.
3) It's the courts' job is to filter out the misinformation and focus on the supportable facts. No personal opinions, beliefs or judgements: Just the facts. Professional opinions are allowed from independent witnesses, who may appear for the defense or prosecution, but are reminded to remain impartial.
4) It is the job of the prosecution and defense to ensure that all pertinent facts are presented.
5) The whole purpose of a trial is to ensure the jury can make an INFORMED decision. Otherwise why bother presenting the evidence to them?
Does that make sense now?