§ 581 Issue of fact arises, when.

When someone pleads not guilty, that creates a factual dispute that needs to be settled at trial. The same thing happens if someone claims they've already been tried for the same crime before, either convicted or found not guilty.

In both situations, the court can't just decide the matter on paper. There are facts in question that a judge or jury needs to sort out. This rule simply identifies the two specific moments in a criminal case when this kind of factual disagreement officially begins.