Using Statistics to Determine Whether Causation is Adequately Proven in Medical Malpractice Actions Involving Multiple Events Preceding the Injury

H. Thomas Watson and Peder K. Batalden

H. Thomas Watson is a partner at Horvitz & Levy LLP. He has served as appellate counsel in the California Supreme Court and Courts of Appeal, the Ninth Circuit, and other jurisdictions. He has extensive experience in health care law, as well as in other areas of substantive and procedural law.

Peder K. Batalden is a partner at Horvitz & Levy LLP, an appellate boutique. He has extensive appellate experience, particularly in the federal circuit courts. Mr. Batalden clerked for Judge Kermit Bye in the Eighth Circuit Court of Appeals, and is a co-author of the Rutter Group’s treatise on handling civil appeals before the U.S. Court of Appeals for the Ninth Circuit. Mr. Batalden is a former chair of the State Bar of California’s Standing Committee on the Federal Courts.

To prove medical malpractice liability, the plaintiff must establish through competent expert testimony that, to a reasonable degree of medical certainty, the plaintiff’s injury was probably caused by the defendant’s negligence. To have evidentiary weight, an expert’s medical causation opinion must be supported by an adequate foundation demonstrating why the expert is reasonably certain that probable causation exists. This article discusses what this standard of proof means, how statistical analysis helps to determine when the standard for proving medical causation has been met, and how causation can be properly established in situations where multiple events precede the injury and each event in the sequence is dependent on the preceding event.¹