Unlike automobile accidents, most medical malpractice litigation involves plaintiffs with substantial preexisting illness. These cases require expert testimony on the issue of causation—the extent that the defendant’s negligence increased the patient’s medical costs. If the patient has a serious chronic disease, it may be impossible to prove that the physician’s negligence increased the cost of the patient’s care. This fact, combined with the patient’s limited earning capacity, makes it very difficult to establish sufficient damages to justify bringing a medical malpractice lawsuit on behalf of an elderly, chronically ill patient.

There are two classes of cases in which the defendant causes an injury independent of the patient’s preexisting illness or condition. A small number are pure accidents, unrelated to questions about medical judgment. Typical of these are slips and falls in the hospital, burns from improperly grounded electrosurgical devices, and the patient’s receiving medications and procedures meant for a different patient. It is usually easy to separate the medical costs of these mishaps from the patient’s overall medical care. The more difficult cases are those in which the patient has a self- limited or curable medical condition and suffers a severe injury from medical treatment—for example, birth trauma cases and anesthesia-related injuries in otherwise healthy persons undergoing elective procedures such as orthopaedic surgery. The plaintiff may have difficulty in proving that the defendant was negligent, but once negligence has been established, the excess medical costs are obvious.