Figure 1

Compact and expanded representations of a Bayesian network for a one stain one offender case. (i) Formal outline of a Bayesian network for evaluating a correspondence (M₁) between the profile of a crime stain and that of a sample from a suspect, according to Equation 3. The setting relates to one in which the population of potential offenders is of size N and either the suspect (H₁) or one of the other N−1 individuals (${\bar{H}}_1$) is the source of the crime stain (proposition H). The corresponding genetic feature occurs in the population with rate γ. (ii) Evaluation of a situation in which the size of the population is N=100, γ is 0.01, and the suspect’s profile is found to correspond to that of the crime stain (M₁). The posterior probability that the suspect is the source of the crime stain, Pr(H₁ | M₁), is shown in the node H. It takes the value 0.5025. Instantiated node states are shown in bold, and probabilities are displayed in percentages.