 First, the prior probability can be equated to \(1/k\) where \(k\) is the number of alternative equiprobable hypotheses. If there are \(k\) possible hypotheses and no one is more probable than the other, it is natural to assign \(1/k\) to each hypothesis. This approach, however, would render prior probabilities quite sensitive to the choice of hypotheses and thus potentially arbitrary. In addition, this approach is particularly unsuitable for criminal cases. If two hypotheses are “the defendant is guilty” and “the defendant is innocent”, the prior probability of each would be 50%. Defendants in criminal cases, however, should be presumed innocent until proven guilty. Prior probability of guilt at the level of .5 seems excessive. The presumption of innocence—a procedural protection afforded to all defendants in many countries—should require that the prior probability of guilt be set to a small value (Allen et al. 1995). But it is unclear how low that value should be. Would .001 be sufficiently low or should it be .000001? All that can be said, perhaps, is that in criminal cases the prior probability of guilt should be extremely low (Friedman 2000).