The procedure known as “invoking the rule”— a rule of civil procedure that allows a party to request that a witness be prevented from hearing the testimony of other witnesses in the trial—can be distressing to witnesses. The intent is to prevent witnesses from refreshing their memory or shaping their testimony to fit other testimony. The rule is particularly frustrating to health care practitioners acting as expert witnesses. They will be asked to testify about the validity of other testimony that they are prevented from hearing. Since the attorneys are free to paraphrase the words of other witnesses, perhaps putting a different cast on them, the expert may be in the position of condemning another physician for something the physician did not say or do.