Perception problems of the verbal scale

Abstract

Many forensic scientists use a verbal scale to describe the significance or weight to be attached to their opinion. Although there is a considerable amount of work in the field of psychology regarding people's perception of quantitative descriptors such as those used in the verbal scale, there has been no published work relating to the use of such descriptors in a forensic context. Our aim was to assess the extent to which the verbal expressions used by the expert in court are perceived and the extent to which they are differentiated by potential jurors. Four hundred volunteers were asked to indicate the level of strength they perceived from the use of the verbal scale characters within excerpts from purported expert witness statements. Although preliminary, these results show that there are serious misunderstandings of the verbal scale. It does not achieve the purpose for which it was created. The terms used are unlikely to be understood properly by lay people and it would appear that they are actually misunderstood.

Keywords: Perception; Verbal scale; Weight of evidence.