 In Evett’s original formulation, two stains from two different sources are left at the crime scene, and the suspect’s blood matches one of them. Let the first hypothesis be that the suspect was one of the two men who committed the crime and the second hypothesis the negation of the first. Evett (1987) shows (see his paper for details) that the likelihood ratio of the match relative to these two hypotheses is \(\slashfrac{1}{2q_1}\) where \(q_1\) is the estimated frequency of the characteristics of the first stain. Surprisingly, the likelihood ratio does not depend on the frequency associated with the second stain.