It is undeniable that the assumption of sincerity is important to assertion, and that assertion is central to the transmission of beliefs through human testimony. Discussions of testimony, however, often assume that the epistemic importance of sincerity to testimony is that of a (fallible) guarantee of access to the actual beliefs of the speaker. Other things being equal, we would do as well or better if we had some kind of unmediated access to the beliefs of the other person, without the risks involved in the overt act of speaking, and the assumption of sincerity in speech is the closest we can come to this access. Contrary to this picture, I argue that sincerity has a quite different epistemic role to play in testimony than that of an indicator of the speaker's beliefs. The epistemology of testimony requires reference to the speaker as agent, and not just the speaker's beliefs, as well as a sense of ‘expression of belief that links it to the specifically addressive relation to another person.