In child maltreatment hearings, the expert's opinion must be objective in the sense that it is based on findings and interpretations from a professional examination. The ultimate test for accuracy and impartiality is a willingness to prepare testimony that can be used unchanged for either the plaintiff or the defendant. In addition to expertise in the relevant subject, the expert is often expected to provide the court with the standards of practice applicable to the specific case. Before agreeing to serve as an expert witness, the health professional should review the following issues with the requesting attorney: the practitioner's views about the case, any biases or potential biases in the case, the nature of the special expertise required in testifying on the case, and the practitioner's expected role. Tips for the clinician as an expert witness in a child maltreatment trial address prehearing preparation, general attitude and demeanor, and responses to questions. The chapter concludes with an outline of the common tactics of cross-examination. The general advice provided in this section is that the cross-examination will attempt to focus on any aspect of the expert's testimony that may weaken the prosecution's case and plant seeds of doubt in the jurors' minds as to the defendant's guilt. Some tactics mentioned in the chapter are friendly, condescending, or belligerent demeanors; the demand for a "yes" or "no" answer to questions that need an explanation; misstating what the witness has just said; attempts to show that the expert's procedures conflict with accepted professional standards; staring at the witness with an extended pause; nonverbal disapproval; implication that the expert is just guessing about a diagnosis; and suggestions of bias and incompetence. A relevant case vignette with follow-up questions is presented. 2 references