The verb morphology of Kashaya, a Pomoan language of northern California, includes a class of five evidential suffixes. All but one ends in the vowel /a/, whose special behavior is the focus of this paper. A central goal is to lay out the facts clearly and thoroughly, since they are not easily available in existing sources; but I also discuss several possible analyses and their theoretical implications. I first present the evidential suffixes, illustrating contexts in which the /a/ is present and absent, along with the facts of the imperative suffixes and the clitic /ʔ/ that accompanies the imperative verbs. The main point of interest is the interaction of this clitic, whose distribution depends on the position of the imperative verb in the sentence, with the evidential /a/, which has the classic properties of lexical phonology. I discuss theoretical issues that arise under various analyses, including a morpheme-specific rule of /a/ deletion, morphosyntactic feature interaction between the word and phrase, and a phrasal phonological rule that is sensitive to the presence of an Evidential Phrase boundary.