One expert to another: “What did your attorney tell you?” “He told me to tell the truth.” “Did he say anything else?” “Yes, he told me what the truth was”
Though expert witnesses have been used for centuries in Europe, they were rare in the United States until the 1920s. The Supreme Court had been cautious in using experts and limited their cross-examination, which was perceived as a waste of time, exhausting and confusing to the court and jury instead of clarifying the issues at hand. 1 Then, in 1923, the United States Circuit Court of Appeals for the District of Columbia Circuit issued a landmark decision that defined the basic prerequisite for admitting scientific evidence and, thus, testimony by expert witnesses.
1 Marcia Angell, Science on trial: The clash of medical evidence and the law in the breast implant case, 1st ed. (New York: W.W. Norton & Company, 1996).