Most witnesses are fact witnesses; they have personal knowledge of either the incident that underlies the lawsuit or the persons involved. Anyone may testify as to facts; only an expert may present opinions. Fact witnesses are usually laypersons who have little experience in the courtroom. Cross-examination is more effective with these witnesses than with experienced expert witnesses.

An expert, such as a physician, may be called as a fact witness in areas that are outside his or her expertise. For example, a physician may have witnessed an automobile accident. A physician may be a fact witness when a case involves a person whom the physician has treated. The physician may be asked to testify as to the fact of the patient’s injury, the treatment rendered, the cost of the treatment, and the current condition of the patient. These are matters of fact contained in the patient’s medical record. Questions about the patient’s prognosis, however, require an expert opinion. It is this requirement of special qualifications to render opinions that separates fact from expert testimony.

The most important fact witnesses in civil cases are the parties themselves. The jurors’ sympathy for the plaintiff versus the defendant is an important determinant of their ultimate verdict. Plaintiffs in medical malpractice cases must convince the jury that they have been injured and that they are deserving of compensation. Defendants must convince the jury that they deserve to be vindicated, both because they did nothing wrong and because they are good people. In criminal trials the dynamic is different. The defendant’s right against self-incrimination means that the defendant may refuse to testify, and frequently does. The victim, if living, may testify, but in many cases the victim is dead or unavailable. In fraud cases, especially reimbursement fraud, the only victim may be a corporation or the government.