Mental health professionals, usually those who have been treating an individual or who are witnesses or bystanders to an event or conversation, may be called as lay witnesses and asked to testify only about facts. In contrast, a psychiatrist who agrees to appear as an expert witness has agreed to perform an evaluation and can offer opinions that aim to guide the court in its decisionmaking. An expert may be called either as a neutral court witness or an adversary expert for one side. The stages in testimony include preparation for the hearing, the process of qualifying the expert through testimony on credentials and experience, direct examination, cross-examination, and redirect and recross-examination. Crucial components of witness effectiveness include grooming and clothing, promptness, posture, and specific techniques in answering questions. Witnesses should also be aware of the hearsay rule and its exceptions. 4 references