Child sexual abuse victims are often not good witnesses because they are frightened and because developmentally and psychologically they are not able to give consistent details of their sexual abuse. Jurors often hold misperceptions of the nature of child sexual abuse, and these are also impediments to accurately assessing crimes against children. The expert witness, then, plays a role in helping judges and jurors to understand and evaluate the testimony of the child witnesses. Expert witness testimony falls along a spectrum of increasingly high impact in identifying the guilt or innocence of the defendant and fits into seven categories: refutation of defense counsel claims; common characteristics of sexually abused children; general veracity of children alleging sexual abuse; veracity of a particular child witness; matching general characteristics of sexually abused children with those of the child witness; common characteristics of sexual abusers of children; and expert testimony on the abuser's identity. Courts should admit expert testimony in all areas of the spectrum except the last, which should be inadmissible because the expert is not competent to testify on the defendant's actions without evaluating the defendant. 242 footnotes.