In a forensic context, credibility judgements are often of critical importance because of the frequency of disputed accounts. Where there is disagreement about what has happened, considerable attention has been paid to ways of determining how much credibility is warranted in detecting deception. Some techniques that have been proposed include the polygraph, Statement Validity Analysis and Scientific Content Analysis. This chapter examines the credibility of accounts from a witness which involve judgements of the accuracy of the witness's memory. Evaluation is problematic because of different factors that are likely to have an influence on the credibility of an account. In general children, and indeed older adults, are poorer than adults from the general population in aspects of encoding, storage and retrieval, but their ability to give accounts is most influenced by how they are interviewed. Particularly important to judgements of credibility is the way in which accounts are elicited.