Expert Testimony
Expert witnesses play a powerful role in the courtroom, butnot everyone who claims to be an expert is allowed to testify. Federal courtsrely on Federal Rule of Evidence 702 to determine when expert testimony isadmissible and whether it can be presented to a jury.
What Is Expert Testimony?
An expert witness is a person who has specialized knowledge,skill, experience, training, or education in a particular field. Unlike a factwitness, who testifies about what they personally saw or experienced, an expertwitness helps the court understand technical or scientific information thatgoes beyond common knowledge.
Expert testimony is used to explain how an injury occurred,whether medical treatment was necessary, how an accident unfolded, or whetherprofessional standards were met. Because expert opinions can strongly influencejuries, courts apply strict standards before allowing this type of testimony.
Federal Rule of Evidence 702
Federal Rule of Evidence 702 governs the admissibility ofexpert testimony in federal courts. The purpose of the rule is to ensure thatexpert opinions presented to a jury are reliable, relevant, and based onlegitimate methods rather than speculation or unsupported theories.
Under Rule 702, expert testimony is admissible only if allrequired standards are met.
The Five Requirements for Expert Testimony
First, the expert’s testimony must help the jury understandthe evidence or determine a fact that is in dispute. If the testimony does notmake the issues clearer or more understandable, it will not be allowed.
Second, the witness must be qualified as an expert.Qualifications can come from education, professional training, specializedexperience, or a combination of these factors. A formal degree is not alwaysrequired, but the witness must demonstrate genuine expertise in the relevantfield.
Third, the expert’s opinion must be based on sufficientfacts or data. Opinions built on incomplete information or assumptions are notadmissible under Rule 702.
Fourth, the testimony must be the product of reliableprinciples and methods. Courts examine whether the expert used acceptedpractices in their field rather than personal theories or untested techniques.
Fifth, the expert must reliably apply those principles andmethods to the facts of the specific case. Even reliable methods can bemisused, and courts carefully review how an expert reached their conclusions.
How Courts Evaluate Reliability
When determining whether expert testimony meets Rule 702standards, courts often rely on a set of factors developed through case law.These are commonly referred to as the Daubert factors.
Courts consider whether the expert’s theory or technique canbe tested and has been tested in practice. They look at whether the method hasbeen subjected to peer review and publication, which helps ensure accuracy andaccountability within the scientific community.
Judges also examine the known or potential error rate of thetechnique, as well as whether there are established standards controlling howthe method is applied. Finally, courts consider whether the theory or techniqueis generally accepted within the relevant scientific or professional community.
These factors help prevent unreliable or misleadingtestimony from influencing a jury’s decision.
Why Expert Testimony Matters
Expert testimony can make or break a case. In personalinjury cases, experts may explain the cause of injuries, the necessity ofmedical treatment, or the long-term impact of an accident. In criminal cases,experts may analyze forensic evidence, mental health issues, or technical datathat directly affects guilt or innocence.
Because expert opinions carry significant weight, Rule 702acts as a safeguard. It ensures that juries hear only credible, well-foundedexpert testimony that is grounded in real knowledge and reliable methods.
The Bottom Line
Federal Rule of Evidence 702 exists to protect the integrityof the courtroom. It ensures that expert testimony is helpful, trustworthy, andproperly applied to the facts of a case. While these standards apply to allfederal courts, not all state courts follow the same framework, making itespecially important to understand how expert testimony is evaluated in eachjurisdiction.
At Ryan, Miller & Coburn, we understand how criticalexpert testimony can be and how important it is to challenge unreliableopinions when they appear. Knowing the rules that govern expert witnesses helpsprotect your rights and strengthens the pursuit of justice.
