The expert’s opinion is one of the most important pieces of evidence in a trial. However, the opinions of experts come with several inherent limitations that can leave them vulnerable to attack by opposing counsel. These include the risk of error or intentional falsehood, which can leave a witness’s credibility in doubt, and the fact that an expert’s conclusions may be unreliable if they are not supported by sufficient corroboration.
In order to meet the Daubert gatekeeping standard, an expert must cite credible sources of information upon which his or her opinion is based. These include journal articles that address the subject of the case, government studies, and reports by others who use the product or service in question (e.g., a medical device user report submitted to the FDA).
Additionally, an expert’s opinion should be based on provable facts and test results obtained through established methods recognized in the field. It is also critical for the expert to have sufficient time to develop a well-supported opinion, as experts must consider their work in a timely manner and often face competing commitments.
As such, it is generally prudent for attorneys to refrain from coaching or discussing the substance of an expert’s opinion in written correspondence with the expert. Instead, a conference call or Zoom meeting to discuss scope and preliminary thoughts is typically the preferred way to communicate with an expert, as it avoids any possible waiver of attorney-client privilege.