A recent Missouri Supreme Court case, Linton v. Carter, will likely have far-reaching implications on defense expert testimony on the issue of causation, particularly in complex cases. Although Linton is a medical malpractice case, the Court’s decision will impact any case where an expert cannot identify the exact cause of an injury with a reasonable degree of certainty other than to dispute the cause cited by a claimant.
Linton involved alleged medical malpractice in the delivery of a baby. The baby was diagnosed with a white matter brain injury known as periventricular leukomalacia (“PVL”) one year after birth. Plaintiffs alleged the defendant doctor delayed delivery while the umbilical cord was compressed, causing loss of oxygen to the baby’s brain and ultimately PVL. A defense expert, the only neonatologist to testify in the case, opined that based on the baby’s symptoms at birth the PVL did not develop during the delivery itself. Instead, the defense expert testified to a reasonable degree of certainty that the PVL was caused by conditions which existed either before or after the delivery, or some combination of them. He could not determine the exact cause or timing. Another defense expert similarly opined the PVL was clearly not the result of something that occurred during delivery, but could have resulted from an intrauterine or post-natal injury, or both. Plaintiffs moved to exclude the first expert’s opinion because he could not identify the exact cause with a reasonable degree of medical certainty. Defendants argued that they do not hold the burden of proof and need not specify the exact cause of the plaintiff’s injuries, but are allowed nonetheless to challenge plaintiff’s theory. The trial court allowed the expert to testify, and a verdict was rendered for the defendants. Plaintiffs appealed.
While there have been cases on alternative causation in the state, they pre-date the Missouri statute on expert opinions, R.S.Mo. § 490.065. This rule now mirrors Federal Rule of Evidence 702, which requires an expert’s opinion to be based on sufficient facts and data, be the product of reliable principles and methods, and apply those reliable principles and methods to the facts. Any expert opinion must help the trier of fact understand the evidence or determine a fact at issue.
The Court reviewed the propriety of alternative causation opinions in light of R.S.Mo. §490.065. Alternative causation testimony can help the trier of fact understand potential causes in complex cases, and, if properly supported, can satisfy the remaining requirements of the statute. If an expert applies reliable principles and methods to the facts of the case, it can help the trier of fact understand the evidence and reach the correct result. Even though the expert cannot establish the exact cause of the injury, the expert can still satisfy the requirements and testify to the opinion.
The Court held that while the standard may apply equally to all parties, the plaintiff bears the burden of proof. A defendant is not required to disprove a plaintiff’s case. The court held that “any rule requiring a defendant’s expert to prove a plaintiff’s injury resulted from a specific cause or combination of causes would improperly shift the burden of proof to the defendant and hinder the defendant’s ability to disprove the plaintiff’s theory of causation.” Plaintiffs, however, must prove causation, and alternative theories of causation are not sufficient in and of themselves. Plaintiffs must present actual, substantial evidence of a connection between the act and the harm that resulted.
While the Linton case was a medical malpractice cause, the Court’s holding will likely have a lasting impact on defendants’ presentation of expert evidence, particularly in complex cases. Defendants are now empowered to employ experts to cast additional doubt on plaintiffs’ claims, even if those experts cannot pinpoint an exact alternative cause of the plaintiff’s injuries. This decision allows defendants to provide evidence of alternative theories of causation, and allows both judges and juries to make informed decisions about the actual cause of the harm.
 No. SC98888, (Mo. banc Nov. 23, 2021) https://www.courts.mo.gov/file.jsp?id=182225