Cross-Examining on Personal Tolerance for Forces Another false comparison defense biomechanical witnesses may use is the analogy of personal tolerance for forces. For example, the witness may state the plaintiff’s injuries could not have been caused by the collision because they are an active person who regularly engages in activities involving greater forces. The defense biomechanical witness is essentially arguing your client is more likely to tolerate injury because they are an active person. This is not necessarily true. A lot depends on how the forces are applied. Running a lot builds tolerance for forces associated with running but does not necessarily make someone more resistant to the kinematics of whiplash. A runner will still get hurt if they walk into a piece of furniture in the dark, even though the speed is slower than they regularly experience. The inherent problem with this testimony is there are no established thresholds for when injury occurs. So, when a defense biomechanical witness testifies they would not expect injury from a collision at 3g’s, it is important to press there is no established threshold for when injury will occur and there is tremendous variability in the general population. There is also tremendous variability based on factors such as direction of impact, type of seat, seat position, type of headrest, headrest position, seating position, height and weight of occupant, etc. which are not factored in determining injury thresholds, making the question impossible to study and thereby establish objective, verifiable, repeatable results necessary to make such a claim. Similarly, defense biomechanical witnesses generally cannot testify on the percentage of risk of injury for any particular individual involved in any particular collision. Is there a 0% change of injury, 1% chance of injury, 90% chance of injury? There is no scientific basis in biomechanical literature to make such a claim. Use All Other Grounds for Cross-Examination of Experts Many defense biomechanical witnesses spend a significant amount of time testifying for the defense and repeatedly find persons bringing lawsuits for personal injuries from motor vehicle collisions could not have been hurt in those collisions. Many do not advertise for business at all and obtain repeat business from word of mouth amongst defense lawyers and insurance companies. Many defense biomechanical witnesses rarely or never testify for plaintiffs. Tying their financial bias and desire for repeat business to their opinions can pull back the curtain and show what is really going on behind the scenes. Often, prior to the defense biomechanical witnesses hiring, no one has ever suggested the plaintiff was not hurt in the motor vehicle collision and it is only the hiring of the defense biomechanical witness that created any argument against causation of injuries. Additionally, all other grounds for cross-examination of lay and expert witnesses are important. The witnesses’ lack of first-hand knowledge, lack of information about the circumstances of the collision, circumstances of the plaintiff and circumstances of the injuries are good subjects for cross-examination. Rebutting Biomechanical Testimony Having a friendly expert to rebut the opinions of the biased defense biomechanical witness can be more effective than cross-examination alone. Defense biomechanical witnesses often testify frequently and have become very good at dodging questions. A doctor or plaintiff biomechanical expert can be an effective way to point out the limitations and fallacies in the defense biomechanical witness’s expert testimony. Here are some of the benefits of calling a plaintiff biomechanical expert: • Your expert can provide a clear and concise explanation of the forces involved in the collision and how those forces caused your client’s injuries. • Your expert can rebut the defense expert’s testimony and point out any flaws in their analysis. • Your expert can help the jury to understand the complex science of biomechanics and how it applies to your client’s case. When choosing a plaintiff biomechanical expert, it is important to select someone who is qualified and experienced in the field. You should also make sure your expert is a good communicator and will be able to effectively explain the science of biomechanics to the jury. The best biomechanical experts are also licensed health care providers so they can testify directly regarding force, kinematics, causation of injury and rule out other potential causes of injury. 1. Johnston-Forbes v. Matsunaga, 333 P.3d 388, 395 (Wash. 2014) 2. Nolet, P.S.; Nordhoff, L.; Kristman, V.L.; Croft, A.C.; Zeegers, M.P.; Freeman, M.D. Is Acceleration a Valid Proxy for Injury Risk in Minimal Damage Traffic Crashes? A Comparative Review of Volunteer, ADL and Real-World Studies. Int. J. Environ. Res. Public Health 2021, 18, 2901. 3. Allan F. Tencer, Ph.D, Understanding and Managing the Impact of Vehicle Crashes: Reconstructing the “Accident,” UW Department of Orthopedics and Sports Medicine, 2008 Orthopedic Research Report. Biomechanical Witnesses continued from p. 39 40 Trial Lawyer | Winter 2025
RkJQdWJsaXNoZXIy Nzc3ODM=