I think a lot of people actually do think, even subconsciously, that it's better for an innocent person to go to prison wrongly than to risk a guilty one going free. As a juror you cannot rely on what your "gut instinct" is telling you. That isn't good enough. You have to look, objectively, at the evidence and ask if it shows you beyond a reasonable doubt that this person definitely committed the crime they are accused of. If it doesn't then you HAVE to find not guilty. It's worrying how many people don't understand that.