William Alston has articulated a powerful defence of the claim that mystical perception generates prima facie justified beliefs about God. At the heart of his defence is the claim that mystical perception is ‘innocent until proven guilty’; that is, Alston claims that the practice of forming beliefs on the basis of putative perceptions of God should be accorded the same presumptive innocence we accord to other standard ways of forming beliefs like sense perception, memory and introspection. But Alston employs a strategy for defending mystical perception that seems to obviate the possibility of criticizing mystical perception and thus that renders otiose Alston's claim that that practice is innocent only until proven guilty. I argue that this appearance is deceptive; Alston's strategy does not render effective criticism of mystical perception unreasonably difficult. I further argue that granting the legitimacy of Alston's strategy is essential to a fair, measured criticism of mystical perception.