In the 'learned treatise' cross-examination approach, the attorney confronts the expert witness with a particular text or professional paper and asks the witness if he/she is familiar with the source and/or regards it as an authoritative document. The attorney's objective is either to cast doubt on the witness' credibility by showing him/her to be unfamiliar with allegedly relevant documents from the supposed expert's field or to cast doubt on the substance of the witness' testimony by showing that his/her professional opinion, conclusion, or judgment is in conflict with another expert. Examples of authoritatively documented assertions often used by attorneys in cross-examination are as follows: (1) the allegedly mentally-ill defendant is not really all that different from most people living independently in the community; (2) mental health professionals cannot distinguish the mentally-ill person from the normal person; (3) psychodiagnosis, which underlies the expert's legal opinion, is too unreliable to justify mental health testimony; and (4) mental health professionals' predictions for future dangerous behavior by defendants are highly inaccurate. Supportive sources for these assertions are listed, along with rebuttal tactics and rebuttal sources. The general substance of the last assertion regarding predicting dangerousness is noted to have no authoritative rebuttal; however, for certain issues, such as the probability of suicide, the relative accuracy of predictions can be supported. The expert witness should be familiar with all professional literature related generally and specifically to the testimony he/she is to give. Clear arguments should be developed to challenge any positions that do not support the testimony. References are provided.