When a judge is making a decision about a fact in a case under the Criminal Investigations (Bodily Samples) Act 1995, they decide based on what is most likely to be true. The judge looks at the evidence and makes a decision on the balance of probabilities, which means they choose the option that seems more probable. You can think of the balance of probabilities like a scale, where the judge weighs up the evidence and decides which side is heavier.