This chapter reviews three knowledge sets that professionals rely on to navigate cases involving child witnesses. The first set includes psychological principles that explain why children’s testimony can be amazingly rich and accurate in some instances and disturbingly inaccurate at other times. The second knowledge set consists of findings about autobiographical recall and suggestibility that describe how developmental principles translate into children’s capabilities and limitations as witnesses. The third knowledge set involves four principles of skilled practice: Expert practice is informed by knowledge of human development, embeds testimony in the context of children’s lives, considers the strength of case evidence when making practice decisions, and is guided by standards and evidence-based protocols. Examples for each of these four principles of skilled practice explain how forensic thinking and practice differ from the habits adults acquire in their everyday lives. Experts need a comprehensive, detailed approach to cases involving child witnesses because autobiographical reports are dynamic products of a developing cognitive architecture interacting with a social world.