How Expert Testimony Works

Expert testimony is an opinion given by an expert on a specific topic(s) relevant to a case being heard in court. Expert witnesses speak truthfully using facts or data while on the witness stand. Questions can be asked by both the party that requested their presence and opposing counsel during cross examination to confirm the expert’s training and experience.

When and why are expert witness testimonies used in legal cases?

Expert testimony is especially helpful in complicated cases where it's difficult for the jury to understand both sides of the claim and come up with a verdict. Experts are called in many types of lawsuits regarding car accidents, construction accidents, product liability and other complex cases. Effective experts help juries understand specific facts to better educate them on the case.

In federal court, according to Federal Rule of Evidence 702, experts may testify at trial in the form of opinion or otherwise if:

• The “expert’s scientific, technical, or other specialized knowledge will help the trier of fact to understand the evidence or to determine a fact in issue;”
• The “testimony is based on sufficient facts or data;”
• The “testimony is a product of reliable principles and methods;” and
• The “expert has reliably applied the principles and methods to the facts of the case.”

Lawsuits involving medical, scientific or mathematical facts may be tough for the jury to fully comprehend. Expert testimony can help jury members make a well-informed final verdict.

Informed verdicts can also pave the way for future litigation in similar cases, especially in bellwether trials. For example, asbestos litigation benefited greatly from expert testimony proving the negative health effects of asbestos exposure. By having experts speak extensively on these dangers, future verdicts may continue to favor the victims of this toxic exposure.

A lawsuit involving a medical drug may retain an expert who is a doctor to discuss the issues with the drug. That doctor can break down how the drug affects the body while also confirming their medical expertise on the topic.

In 2020, a judge ruled that expert testimony could move forward in Johnson and Johnson talcum powder litigation. The judge ruled that the plaintiffs’ experts can testify at trial regarding various studies that have shown talc-based products can cause cancer, potentially due to asbestos, fibrous talc or heavy metal contamination.

Social media harm litigation also utilized expert testimony in a recent trial. Dr. Anna Lembke, psychiatrist and Stanford University professor, was called to the stand by a California woman who alleges Meta created their social media platforms to be addictive. Dr. Lembke affirmed this claim by explaining her knowledge of addiction as a therapist. This clearly resonated with the jury as the verdict ruled in favor of the California woman. Dr. Lembke also similarly testified in the landmark $375 million verdict on behalf of the State of New Mexico versus Meta.

Motley Rice attorneys have litigated and investigated complex cases across the country. We have the experience to adapt to trial processes and requirements in any jurisdiction to hold the responsible parties accountable for their actions.

Our team has experience litigating cases involving:

• Toxic exposure
• Sexual abuse
• Diabetes
• Medical devices

Read more on our complex litigation experience.