A hierarchy of propositions: deciding which level to address in casework

In a previous paper in this journal (Cook R, Evett IW, Jackson G, Jones PJ and Lambert JA. A model for case assessment and interpretation. Science & Justice 1998; 38: 151-156), the authors described a model for case assessment and interpretation. An essential element of the model, indeed of any interpretation, is that of framing a pair of propositions to weigh against each other. It is one of the functions of the scientist to determine, in the light of the evidence that is found and of the circumstances of the case as they appear at the time, the pair of propositions that can realistically be addressed. It is helpful to consider a broadly-defined "hierarchy of propositions': In general, the higher the level of the propositions, the greater the assistance that will be given to the court but, of course, the scientist may not stray outside the bounds of his/her expertise nor, indeed, into the realms of advocacy. This paper, a continuation of the first, discusses the hierarchy of propositions by means of case examples.