Expert witnesses undoubtedly know a great deal about topics on which ordinary people lack information. But experts, no less than other people, are subject to predictable memory biases. No plaintiff lawyer can enter the courtroom alone, without a doctor by his or her side to serve as an expert witness. The behavior of the plaintiff's experts (and the behavior of the experts who walk alongside the defense lawyers as well) is the subject of this article. What should guide expert testimony? How should those guidelines be implemented? How has our profession dealt with these issues?