Expert testimony is critically important in personal injury cases to prove what caused the accident and the full extent of the victim’s injuries. Our attorneys often use accident reconstruction experts, as well as medical experts. Indeed, many cases turn into a “battle of the experts” with witnesses for each side offering competing theories and conclusions. But, since the role of the court is to search for the truth — and not simply bend to impassioned advocacy — there are strict rules that govern expert testimony in the state and federal courts. Here are some basic rules for expert testimony in New York courts:
- Qualifications as an expert — The trial court has discretion to decide whether an expert has the requisite qualifications to render an opinion.
- The “Frye” standard — First articulated in a 1923 case, an expert’s opinions must be generally accepted within the expert’s field. For example, the Frye court rejected evidence of a polygraph test, stating that “the thing from which the [expert’s] deduction is made must be sufficiently established to have gained general acceptance in the particular field in which it belongs.” Since polygraph tests were (and remain) controversial, the court determined the tests had not gained “general acceptance” and the results would be inadmissible. Under the Frye standard, an opposing party can object that an expert’s testimony amounts to a “novel theory” that the professional community does not widely share. Expert testimony that reflects a minority opinion within a profession is barred under the Frye standard.
- Disclosure of expert witnesses under CPLR 3101(d) — Although this statute requires parties to disclose the identity of their expert, it does not set a strict time limit for doing so. Moreover, the law does not require a party to disclose an expert’s report prior to its admission into evidence, nor does it require an expert to be available for a deposition.
- Sufficient basis for an opinion — An expert’s opinion must be based on facts in the record or personally known to him. An expert opinion that is speculative, contingent or merely possible lacks reliability and is not admissible.
- Inadequate foundation — Case law allows a party to challenge the scientific methodology of an expert’s testing procedures. A court may preclude testimony where the expert’s methods for reaching a conclusion are questionable.
- Hearsay — An expert must base an opinion on facts presented at trial or personally known to the expert, or the court can bar that opinion as hearsay. The expert can offer an opinion based on out-of-court evidence when the information comes from a source that is professionally reliable or from a witness subject to cross-examination.
Working with expert witnesses is highly technical and nuanced, and not simply from the legal perspective, where an attorney must make timely procedural maneuvers to get testimony admitted or excluded. Expert testimony is complex in its substance, and a good attorney must direct an expert to deliver scientific findings in a manner that is comprehensible and persuasive to average people outside the expert’s professional field. This is why injured plaintiffs always want an attorney with experience in cases like their own.