Expert Testimony – Proving Causation in a Medical Malpractice Case

The plaintiff must usually rely on expert medical testimony to prove the element of causation in a medical malpractice case unless the issue is clear to even a lay person, e.g., the physicians accidentally amputated the wrong foot, or a pair of surgical scissors is left in the abdomen after an operation.

Because of the complexity of the subject matter of medical malpractice cases, the plaintiff’s use of expert medical testimony helps the jury understand whether violation of the standard of care to which medical treaters are held led to an avoidable bad outcome. Many medical issues are not within the common knowledge of the jury or the plaintiff, so an expert’s testimony can help the jury understand the applicable standard of care and whether the defendant provider failed to meet that standard of care, causation, and damages.

Medical malpractice cases often come down to a battle of the experts. Both the plaintiff’s and the defendant’s experts will offer opinions on the plaintiff’s underlying condition, defendant’s actions, whether defendant’s actions conformed with the applicable standard of care, and whether the defendant caused plaintiff’s injuries. The plaintiff’s expert proof on causation must establish causation by a preponderance of the evidence (to a reasonable degree of medical probability), i.e., The harm was avoidable had the defendant adhered to the standard of care.

A mere “loss of chance” of survival case in a delayed diagnosis of cancer has been held by the California Supreme Court not to satisfy the burden of proof on the issue of causation because the plaintiff had less than 50% chance for meaningful survival even though the defendant was negligent.