The jury decide on guilt or innocence, and their decision is based upon the evidence in front of them. Their interpretation of the facts is their own affair, and is not subject to the directions of the Judge. But they must accept what the Judge tells them on a point of law. This means there will be cases where there is no possible verdict except 'not guilty'. Occasionally there will be a trial within a trial, where the prosecution and the defence argue a point of law to the Judge. This is done without the jury being present, so that they do not become biased. Afterwards, the Judge may recall the jury just to direct that because of the point of law, they must acquit.