In every personal injury case, it is necessary to establishproof of the cause and effect relationship between an accident andthe plaintiff's claimed injuries. Of course, the burden of suchproof rests with the plaintiff. The advances in science andtechnology in the past years have produced tools to facilitate amore objective assessment of the causation issue in litigation. Forexample, given the advent of MRI and CT technologies, a radiologistcan distinguish between signs of acute trauma and chronic,pre-existing degenerative conditions. Moreover, the development ofbiomechanical engineering has provided the basis for a scientificanalysis of causation in appropriate cases.

In New York, the task of proving the essential element ofcausation ordinarily falls to the plaintiff's doctor in personalinjury trials. This doctor's testimony advises that the accidentwas “the competent producing cause of the injury.” Usually thiscausal connection is stated with “a reasonable degree of medicalcertainty.” However, the doctor's “certainty” of the causal linkmay often be based on incomplete data or subjective beliefs thatare not necessarily supported by an objective analysis of thecircumstances of the accident. Medical experts routinely base theiropinions of the causal nexus between the accident and injury solelyon the plaintiff's subjective verbal description of the event,usually provided at the initial visit.

“Reliability” is the chief criterion for admissibility of adoctor's testimony on causation in New York. As we'll discussahead, biomechanical engineering calls into question thereliability of medical testimony on this essential element of thepersonal injury lawsuit.