What is the Role of an Expert Witness in a Negligence Claim?

A negligence claim, in the general legal definition of the term, refers to any claim that alleges a defendant breached the necessary standard of care and that said breach proximately caused plaintiff’s injuries.

Anjelica Cappellino, J.D.

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— Updated on April 27, 2022

What is the Role of an Expert Witness in a Negligence Claim?

Negligence claims can be as broad and varied as practice areas themselves, with almost all tort suits revolving around some form of a negligence theory. As negligence can form the basis of a variety of claims, ranging from medical malpractice to products liability, oftentimes the subject matter at issue will be complex or scientific in nature. In which case, an expert witness will be needed to sufficiently explain the information to the jury.  However, expert witnesses are not necessarily given free range to testify as to their opinion of the defendant’s negligence. Any opinions concerning the defendant’s conduct should be based on the witness’ particularized knowledge on the subject matter and the requisite standard of care. Thus, in order to effectively utilize an expert witness in a negligence case, it is important to be aware of the parameters of their testimony.

How Can an Expert Help a Negligence Case?

The most important testimony an expert can offer in any negligence case is whether the defendant breached the requisite standard of care and if such a deviation caused the plaintiff’s injuries. But first and foremost, the standard of care must be established. Generally, a defendant has a duty to exercise a level of care that a reasonably prudent person in their particular circumstances would exercise. In many cases, this standard needs to be defined for a jury. Interestingly, there is little guidance as to particular standards of care within each practice area. For example, in professional negligence claims, i.e., claims against individuals acting in certain professional specialties such as doctors, lawyers, and accountants, the defendants have a duty to conduct themselves as a reasonable person would in their particular line of work. When establishing the standard of care that a defendant was required to meet, it is important to find an expert that intimately familiar with not just the defendant’s occupation, but also the particular sub-specialty. For example, in a legal malpractice action against a divorce attorney, it would be wise to retain a legal expert in the field of divorce law to testify to the standard of care when handling these particular types of cases.

Whether a defendant breached the requisite standard of care and whether such a breach proximately caused the plaintiff’s injuries is naturally the next question in an expert’s testimony regarding negligence. But like the definition of the standard of care, deviations of said standard are equally dependent upon the particular field at issue. For example, in medical malpractice actions, “any act or omission by a physician during the treatment of a patient that deviates from accepted norms of practice in the medical community and causes an injury” is considered a breach of the standard of care. Naturally, whether a defendant breached his duty is case-specific. Importantly, negligence is not established from a poor result. For example, in a negligence action against a surgeon, it is not enough to show that a patient’s illness was not remedies after the surgery. Likewise, negligence is not proven if the expert simply disagrees with the defendant’s particular approach. Rather, an expert would need to explain how the surgeon’s actions, if at all, deviated from the required minimally competent care.

To prove the defendant’s conduct proximately caused the plaintiff’s injuries, an expert must link the allegedly negligent action with the harm sustained by the plaintiff. For example, in a car accident case whereby the plaintiff was pedestrian hit by defendant’s speeding car, the expert would need to establish that 1) the defendant was negligent in driving at an excessive speed and 2) the excessive speed with which the plaintiff was hit caused the injuries.

Though sometimes used interchangeably, it is important to remember the distinction between factual and proximate causation. While there may be some factual connection between the defendant’s actions and the plaintiff’s injuries, proximate cause addresses the legal (and practical) implications of holding individuals responsible only for conduct that was a foreseeable consequence of their actions. The concept of foreseeability is a cornerstone of proximate cause. In other words, the connection between the defendant’s negligence and the plaintiff’s injuries should not be too attenuated or far-fetched in nature whereby one could not have reasonably foreseen such a result. For example, an auto manufacturer’s negligence in designing its tanks, which cause gasoline to stream outside the vehicle, may cause harm to the owner and passengers.  However, a person passing by the leaking tank who decides to throw an open flame onto the gasoline and start a fire, though grossly disturbing, is not a foreseeable consequence of the manufacturer’s faulty design. As such, when testifying to whether a defendant’s conduct proximately caused the plaintiff’s injuries, an expert should be equipped to opine as both the factual causation and foreseeability of the defendant’s negligence.

Overall, the legal theory of negligence and the general concepts of standard of care have evolved over the years and vary throughout practice area. The more familiar an expert is with the particularized circumstances of a negligence claim, the more likely that the expert’s testimony can help prove the case.

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