Typically you are instructed not to seek any information about the case at hand and if you hear anything about the case unintentionally to inform the judge. Ignoring this is (often) a contempt of court. If the case is serious (or high-profile) enough, you will be sequestered (look for the OJ Simpson trial to see how far that went, though probably never again) so that you don't have access to those items.
A jury decides a case based on the evidence presented and their judgment, not additional evidence that would (may) have been otherwise excluded from the case (and likely was, otherwise you would have seen it as one side or the other would see it as beneficial to bring it up).