The general purpose of expert testimony is to help clarify issues of fact that are beyond the purview of the typical fact finder. Obviously, the types of experts needed on a case are wholly dependent on the litigation subject matter. Experts need not testify to topics solely scientific in nature, but can also testify to any subject that requires technical or other specialized knowledge.
The proliferation of experts on both scientific and non-scientific matters has resulted in cases oftentimes hinging on the testimony of a party’s experts. But exactly how many experts are enough? Since experts are needed to establish liability and the appropriate amount of damages, in many instances, it is prudent to retain an additional expert to establish these elements of a case.
Establishing or Disproving Liability
In any case where the plaintiff is seeking damages from the defendant, the plaintiff must not only prove that the defendant committed the alleged wrongdoing but must also establish the causal link between the defendant’s conduct and the sustained harm. While a plaintiff might offer expert testimony concerning the underlying scientific facts at issue, an expert retained for the sole purpose of establishing liability can bridge the gap between the science and real-world application.
For example, in order to establish liability in a medical malpractice cause of action, the plaintiff must prove that the defendant deviated from accepted standards of practice and that the deviation was a proximate cause of the plaintiff’s injuries. Plaintiffs will undoubtedly offer medical expert testimony to prove their injuries, which may be more or less in-depth depending upon the severity and permanency of the damages. But the neurologist who conducted the plaintiff’s brain scans, or the cardiologist who has monitored the plaintiff’s heart condition, may not be in a position to opine as to whether the plaintiff’s injuries were proximately caused by the defendant. Rather, a medical expert in that field would need to testify as to how the defendant deviated from the requisite standard of care within their respective professions and that the negligence caused the plaintiff’s injuries. In the medical context, this may refer to misdiagnoses, surgical errors, or follow-up treatment failures.
It is not sufficient to assert that the defendant’s actions may have caused the plaintiff harm. In order to be hold the defendant liable, the plaintiff must prove proximate causation, that is, cause that is legally sufficient to establish defendant’s liability under the law. Establishing proximate causation is not always easy, as it can be affected by other contributing factors, such as plaintiff’s prior health history or other treatment choices. But there are ways to apply scientific principles to more accurately determine causation.
For example, in cases involving accidents, such as automobile collisions, causation forensics is an area of study that uses science to determine the causal factors of an accident. On the defense side, an expert should be able to attest to contributing factors that can ultimately break the causal link between the defendant’s conduct and plaintiff’s injuries. In a products liability case, for example, a human factors expert may testify to the ways in which average people handle the products at issue and how such interactions could have influenced the damages sustained from the product.
Whether an expert is meant to establish proximate causation or break any causal connection, it is important that the witnesses avoid common pitfalls. Most importantly, there is a difference between causation (especially proximate causation!) and correlation. As such, experts should make knowledgeable determinations based on the available data and findings at hand.
How Much is the Injury Worth? Bring in the Damages Experts
Damages experts are critical in quantifying the value of the harm caused and determining the monetary amount that should be awarded to the plaintiff. Although damages experts can also testify to liability and causation—typically in cases where the loss is more easily quantifiable in relation to the harm, i.e., a breach of contract involving lost profits—damages experts do not establish causation in many cases. Rather, they explain the plaintiff’s losses.
When the plaintiff has suffered personal injuries, for example, a damages expert can break down and justify the amounts sought, such as compensatory damages, lost earnings, medical expenses, pain and suffering, as well as estimated future losses. Damages experts can also establish the value of loss of consortium (the deprivation the plaintiff’s family or spouse has experienced due to the plaintiff’s injuries).
In terms of purely economic loss, financial experts within the specific industry of the plaintiff can be useful. For example, trademark infringement suits or defamation claims would require the expert to quantify the harm caused to the individual or entity in the past and in the future. If such claims affect a business’s sales and profits, the expert needs to show exactly how while also isolating any other contributing factor.
Overall, the importance of liability and damages warrants the use of additional expert witnesses on your team. While a substantively knowledgeable expert may educate the jury on the subject matter at issue, that is only half the battle. Establishing (or disproving) proximate causation and damages is necessary in order to achieve a successful outcome.