We all have a constitutional right not to incriminate ourselves, or give evidence against ourselves. Just like on TV, when people rely on the 5th amendment to invoke their right to remain silent. The state has to prove it's case without making you help. Of course, they can use anything you do say against you, like Casey's statements before she was in custody or asked for a lawyer. It only applies in criminal cases, big or small, where the state has the power to deprive you of your life and liberty. In a civil case, where private litigants are involved, there is no threat of the state putting you in jail, etc. If you refuse to participate and answer proper questions, inferences can be drawn against you from your silence. It can be a lot more complicated, but I tried to put this in a lay person friendly form. Any help?[/QUOTE
Preponderance of the evidence is the standard in civil cases, whereas beyond a(any) reasonable doubt is the gold standard jury instruction in a criminal case.