Biomechanical Expert’s Testimony on Medical Causation Rejected

What is the permitted scope of testimony of a biomechanical expert in a car crash case?  The Kentucky Supreme Court has given some guidance on the issue.

In Renot v. Secura Supreme Ins. Co., 2021-SC-0281-DG (Ky. June 15, 2023), plaintiff claimed injuries in a motor vehicle collision.  The defendant driver settled out, and the case proceeded against plaintiff’s underinsured motorist’s carrier.   The carrier contested the nature and degree of injuries alleged by the plaintiff, calling both a medical doctor and a biomechanical engineer as witnesses.

The defense doctor said the injuries caused by the wreck were minimal and the plaintiff’s problems were caused by preexisting osteoarthritis.

The biomechanical expert, David Porter, Ph.D., “offered relatively little information [at trial] regarding biomechanical forces and generalized injury potentialities, but instead was permitted to embark on a wide-ranging review of Renot’s medical history and to express his opinion that Renot’s injuries were unrelated to the collision.”  Id. at *4.

The jury returned a verdict for the UIM insurer. The KY Court of Appeals affirmed.

The KY Supreme Court reversed, “conclude his testimony went beyond the appropriate scope of his
credentialed expertise.”  Id. at *6.

The Court said

a qualified biomechanical expert may be utilized at trial to support or discredit a physician’s medical conclusions concerning causation by offering objective, scientifically based testimony
regarding the likelihood or probability that a particular traumatic incident could or would normally be expected to have produced or resulted in a specific medical injury or condition. However, a biomechanical expert may not invade the province of a physician’s absolute authority by conclusively opining whether the traumatic incident at issue did or did not, in fact, cause the medically diagnosed injury or condition of a particular plaintiff. Though a
biomechanical expert may possess the education and training necessary to provide science-based data and statistical information tending to confirm or impeach medical causation as determined by physicians, they are not qualified nor authorized to reach a medical diagnosis or offer their own analogous or antithetical medical conclusions regarding causation based on such information.

Id.  at *8.

Here, the trial court ruled in limine  in accordance with the above rule but then permitted the expert to testify in on medical causation.  The Court ruled that permitting the expert (over objection from plaintiff’s counsel) to deviate from the prior ruling restricting his testimony was error.  Here is an explanation of the Court on how far Mr. Porter was permitted to go in his testimony:

More particularly, in addition to speculating Renot’s knee injury could have been caused by a fall down some stairs and that neck injuries sustained in low-speed car collisions should resolve within five weeks, Dr. Porta was erroneously allowed to testify that Renot’s:

• failure to request an ambulance or visit the emergency room immediately after the collision led him to conclude the knee injury was unrelated to the crash.
• delay of five weeks prior to seeking any treatment was “an awfully long time to go without treatment,” leading him to conclude the knee injury was not caused by the collision.
• inconsistent post-accident complaints convinced him the collision and knee injury were unrelated.
• “long history of knee issues” likely caused her current knee pain.
• genetics and advancing age made it “pretty clear” she is “one of those people unfortunately” suffering from accelerated osteoarthritis which preexisted the collision.
• medical records disclosed physical processes which “are not things that happen overnight” but develop “over a long time.”

During his testimony, Dr. Porta used an exemplar knee to explain the various knee conditions discussed in Renot’s medical records. Secura also utilized Dr. Porta to admit medical records and explain Renot’s medical history. None of this testimony referenced biomechanics or otherwise implicated Dr. Porta’s expertise.

Though admitting, “I’m no physician,” Dr. Porta did not hesitate to opine “when I saw the first complaint was ten weeks later and there was no mention of the accident, they did not appear related to me.” And while making a cursory reference to a biomechanical absence of “sufficient force,” he provided an unauthorized medical opinion regarding causation when he testified “I don’t see any relation between this accident” and Renot’s physical condition. Dr. Porta proceeded to exclude any possibility of medical causation when he testified that any bruising sustained in the collision was incapable of impacting

any of the deeper structures, and certainly not the cartilage inside of here, what you’re seeing is bare bones [holding and pointing to exemplar knee], but there’s an awful lot of tissue still over top of this, there’s tendons we don’t see at all, there’s fat, there’s skin. So, bruise to the area, no problem, that’s certainly possible. But I don’t see any force for deeper tissue injury.

This testimony exceeded Dr. Porta’s well-established qualifications as a biomechanical expert and erroneously invaded the exclusive province of medical doctors in determining medical causation.

Id. at *10-12.

In summary,

Dr. Porta’s lack of appropriate medical credentials should have prohibited him from testifying regarding the presence or absence of any specific and concrete causal connection between the forces incurred in the subject low speed rear-end collision and Renot’s medically diagnosed conditions. Here, the trial court correctly so held prior to trial, but then inexplicably and erroneously permitted such testimony at trial. This failure to follow its own well-founded mandate constituted an abuse of discretion. The biomechanical expert testimony regarding medical causation offered by Dr. Porta should have been disallowed and the error cannot be deemed harmless. The Court of Appeals erred in holding otherwise.

Id. at *12.

Obviously, this KY opinion is not controlling law in Tennessee.  However, it can be used to help guide Tennessee lawyers on how to properly use biomechanical experts in Tennessee case.   My guess is that Tennessee courts would impose similar restrictions on biomechanical experts who lacked a medical degree.


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