Case pre-assessment and review in a two-way transfer case

In previous papers 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. Cook R, Evett Mi, Jackson G, Jones PJ and Lambert JA. A hierarchy of propositions: deciding which level to address in casework. Science & Justice 1998; 38: 231-239], the authors have described a model for case assessment and interpretation. This paper continues the discussion by studying the pre-assessment stage in more detail, using a hypothetical fibres case in which there may be a two-way transfer. It is demonstrated that a simple multiplication of likelihood ratios for the two directions of transfer is not valid because of dependencies in the numerator. The solution to this problem is described by means of a is made. Next the paper shows how the pre-assessment is made. Next the paper shows how the pre-assessment can be updated when a staged approach is taken: the results of the examination of one of the garments are used to inform the decision about whether the second garment should be examined.