 This definition is formulated in a probabilistic language. Legal probabilists interpret it using the likelihood ratio, a standard probabilistic measure of evidential relevance (Aitken et al. 2010; Aitken and Taroni 1995 [2004]; Lempert 1977; Lyon and Koehler 1996; Sullivan 2019). The likelihood ratio (discussed in  Section 2)  is the probability of observing the evidence given the prosecutor’s or plaintiff’s hypothesis, divided by the probability of observing the same evidence given the defense’s hypothesis.