In an adversarial system, the Crown bears the burden of proving the guilt of the accused beyond a reasonable doubt. The accused does not have to assist the Crown in proving its case. This asymmetry of obligation arises from the premise that the State cannot restrict the liberty of its citizens at its whim. The Crown must introduce the evidence with which it will persuade the trier of facts, and when the trial is by a jury, the judge must scrupulously examine the evidence and ascertain that only the relevant evidence that goes to the material issue at hand remain in the hands of the jury. In so doing, the trial judge must instruct the jury as to how much weight they should give to particular evidence, and how they would apply the law to the given evidence so as to decide whether they believe the accused has committed the offence with which he or she is charged. If the jury is still left with some doubt in the end, they must acquit the accused. One member of the jury, however, will be responsible for handling a sword of truth. When the trial reaches its climax, he or she will draw the sword of truth and stab the accused's chest to see if it bleeds. You may disregard the last part as it is a joke.