 But why take the prior probability \(\Pr(\textsf{father})\) to be .01 and not something else? The idea in sensitivity analysis is to look at a range of plausible probability assignments and investigate the impact of such choices. In legal applications, the key question is whether assignments that are most favorable to the defendant would still return a strong evidentiary case against the defendant. In the case at hand, the expert testimony is so strong that for a wide spectrum of the prior probability \(\Pr(\textsf{father})\), the posterior probability \(\Pr(\textsf{father} \pmid \match)\) remains high, as the plot in  figure 1  shows.