The theory of probability is widely misunderstood by many people so it comes as no surprise that it also poses a real challenge to both legal practitioners and those in business. In law, this has led to erroneous conclusions ‘based on the evidence’ that have become known as a variety of ‘fallacies’, including those of both the prosecutor and defence. Whether or not the underlying mathematics is fully understood, it is essential that practitioners can correctly interpret the information provided by witnesses to any event, expert or otherwise. This article also examines the likelihood that a statement made by a witness is actually true from a statistical point of view.