The author's first mistake as an expert witness was to agree to testify without reviewing the documentary evidence to determine a working hypothesis of fault before listening to the attorney's theories. His second mistake was not learning enough about the case before determining, in consultation with the attorney, whether he had the requisite expertise, interest, and ability to be an effective witness in the case. The third mistake was agreeing to testify in an area outside of his specialized expertise, and the fourth error was letting his attorney friend define the area of investigation based on his own theory of the case. Being too aggressive and one-sided in his testimony was the fifth mistake. The author also erred in giving unclear testimony marked by technical and erudite language that tended to confuse and alienate the jury. The author's central advice to attorneys in managing prospective expert witnesses is to have them conduct independent investigations to arrive at their own theories of the case.