Lay factfinders do not understand that rape is a traumatic experience from which some victims never recover, and lay people are ignorant of the anomalous symptoms that some rape victims manifest, symptoms which psychiatric researchers have grouped under the rubric 'rape trauma syndrome.' The scientific community has accepted the RTS theory as valid. If the prosecution uses it as substantive evidence of the rape's occurrence, however, courts generally exclude it on the ground that its prejudicial effect outweighs its probative value. On the other hand, if the prosecution uses RTS testimony as credibility evidence, courts will admit it. If the defense tries to impeach the victim by suggesting that her behavior was inconsistent with that of a 'normal' rape victim, the prosecution should be allowed to present an alternative scientific view of that behavior. Accordingly, so long as the court limits RTS evidence to rehabilitation use, the probative value of the RTS outweighs whatever prejudicial effect such evidence might have. 162 footnotes.