Commentary on Sections Part 11 - Evidence Chapter 1 : Evidence of Bad Character Section 109: Assumption of truth in assessment of relevance or probative value
389.Section 109 requires a court, when considering the relevance or probative value of bad character evidence, to assume that the evidence is true. This reflects the distinction between the roles of the judge and jury: it is for the jury to form a view on matters of fact, such as the reliability of the evidence, and for the judge to rule on issues of law. However, there may be occasions where evidence is so unreliable that no reasonable jury could believe that it was true. In these circumstances, intended very much to be exceptional cases, Section 109(2) makes it clear that the judge does not have to assume the evidence is true. In making this decision, the court should normally make its decision based on the papers before it; however there may be exceptional circumstances in which a separate hearing on the issue (a voir dire) might be necessary. This reflects the current common law position as established in R v H [1995] 2 AC 596 which considered the admissibility of similar fact evidence in cases of alleged collusion.