 Second, legal probabilists can appeal to the reference class problem (Colyvan, Regan, and Ferson 2001; see also later   Section 7). An individual may fall under different reference classes. If 3% of those who smoke have lung cancer and 0.1% of those who exercise regularly have lung cancer, what about someone who smokes and exercises regularly? In Gatecrasher, it is arbitrary to single out the group of people at the stadium and not the group of people with a history of trespassing. There is no clear reason why one or the other reference class was chosen. The choice of another reference class could have led to a different conclusion about the defendant’s probability of liability. This approach has also been endorsed by scholars who are decidedly opposed to legal probabilism (Allen and Pardo 2007). Critics of this approach note that the reference class problem affects any evidence-based judgment. In assessing the strength of any piece of evidence, different reference classes can be used, say the class of witnesses who give detailed descriptions of what they saw or the class of witnesses who are nervous (Redmayne 2008).