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GPSolo Magazine

GPSolo May/June 2024: The Changing Face of Evidence

Qualifying an Expert Witness

Holly Nicole Werkmeister


  • Before expert witnesses can testify in court, they must undergo a rigorous process of qualification to ensure that their testimony is relevant and reliable.
  • According to Federal Rule of Evidence 702, a witness must demonstrate the necessary knowledge, skill, experience, training, or education to qualify as an expert.
  • Voir dire is the procedure by which a lawyer qualifies an expert witness via a direct examination to elicit information to satisfy Rule 702.
Qualifying an Expert Witness
Heide Benser via Getty Images

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In legal proceedings, the testimony of expert witnesses plays a pivotal role in shaping the outcome of cases. Whether in civil litigation, criminal trials, or administrative hearings, expert witnesses lend their specialized knowledge to help judges and juries understand complex issues and make informed decisions. However, before expert witnesses can testify in court, they must undergo a rigorous process of qualification to ensure that their testimony is relevant and reliable. Qualifying an expert witness is a complex topic. At some law schools, advanced evidence classes devote an entire semester to the issue, and there are whole treatises and textbooks written on this single area of the law. This article covers the basics.

Case Law and Rules of Evidence

Several seminal cases have shaped the standards and criteria for admitting expert witness testimony. The first was the 1923 Supreme Court decision Frye v. United States, 293 F. 1013 (D.C. Cir. 1923), followed by the 1993 Supreme Court decision Daubert v. Merrell Dow Pharmaceuticals, Inc., 509 U.S. 579 (1993), which largely supplanted the standard set forth in Frye. In the landmark case of Daubert, the Supreme Court held that trial judges must act as gatekeepers to ensure that any scientific testimony is both relevant and reliable, and the Court set forth factors by which to evaluate the admissibility of expert testimony, including whether the methodology underlying an expert opinion can be tested, whether it has been subjected to peer review, its known or potential error rate, and whether it has gained general acceptance in the relevant scientific community. In Kumho Tire Co. v. Carmichael, 526 U.S. 137 (1999), a case that built upon Daubert, the Supreme Court clarified that the Daubert standard for admissibility applies not only to scientific testimony but also to all expert testimony, even if it is not scientifically based.

These cases, among others, helped establish the framework for the admissibility of expert witness testimony in both federal and state courts, along with Federal Rule of Evidence 702 and its state counterparts. According to Rule 702, a witness who is qualified as an expert through knowledge, skill, experience, training, or education may provide opinion testimony if (1) the expert’s scientific, technical, or specialized knowledge will help the trier of fact understand the evidence or determine a fact at issue in the case, (2) the opinion testimony is based on sufficient facts or data, (3) the testimony is the product of reliable principles and methods, and (4) the expert has reliably applied the principles and methods to the facts of the case to arrive at their opinion.

Voir Dire

Voir dire is the procedure by which a lawyer qualifies an expert witness at trial. The lawyer proffering a witness as an expert conducts a direct examination to elicit information to satisfy Rule 702’s requirements, and then the opposing lawyer may challenge the expert’s qualifications through cross-examination. After voir dire, the trial judge will rule on whether the expert’s opinion testimony is admissible.

While a voir dire will look different depending on the area of specialty that the proposed expert will testify about, there are certain common elements. The hypothetical voir dire questions in this article are based on a proposed medical expert who specializes in orthopedic knee surgery.

Establishing Background, Training, and Skills

Questions to establish that the doctor has the knowledge, skill, experience, training, or education to provide an expert opinion would look something like this:

Q: Please state your name and occupation.

A: Dr. Elena Lujan. I am an orthopedic surgeon specializing in knee surgery.

Q: Describe your educational background and training related to orthopedic knee surgery.

A: I graduated from Western State Medical School, completed a residency in orthopedic surgery at County Hospital, then finished a fellowship focused on knee surgery at Orthopedic Institute. I also serve as a faculty member at Western State Medical School, where I teach about surgical knee procedures.

Q: Can you provide an overview of your experience performing knee surgeries?

A: I have been doing knee surgery for about 15 years. I perform about 100 knee surgeries a year, including such procedures as ACL reconstructions, meniscal repairs, and total knee replacements.

Q: Do you have any board certifications?

A: I am board certified in orthopedic surgery by the American Board of Orthopaedic Surgery.

Q: Have you published any articles or conducted any research related to knee surgery?

A: I have authored several peer-reviewed articles focusing on various aspects of knee surgery, including outcomes research and advancements in surgical techniques.

Q: Have you ever testified as an expert witness in knee surgery cases before?

A: I have provided expert testimony in approximately ten cases involving knee injuries and surgeries.

The trial judge has broad discretion to determine whether a proposed expert is sufficiently qualified, and the witness need not have qualifications in all areas. Therefore, for example, a physical therapist may be qualified to give an opinion about the impact of an injury on the ability to do certain types of work by virtue of experience, even though this physical therapist is not educated or trained as a doctor. Likewise, a recent medical school graduate may qualify as an expert by virtue of education alone, even without any clinical experience. Weaknesses in a proposed expert’s qualifications generally go to the weight, not the admissibility, of the testimony.

In addition, a witness need not have qualifications in a specific specialty area to qualify as an expert. Therefore, an orthopedist who does not perform surgery could still possess relevant expertise to testify as an expert regarding surgical negligence. For example, an orthopedist with training and experience in diagnosing and treating musculoskeletal conditions may qualify to provide an expert opinion as to whether surgery was reasonable or necessary based on familiarity with surgical procedures, as well as their risks and outcomes. However, if the case involves a highly specialized procedure or a rare surgical technique, the court may prefer testimony from an expert who has extensive experience in that subspecialty. A challenge to a proposed expert’s qualifications in such a case might involve the following questions:

Q: You do not have any surgical experience or training?

A: Correct.

Q: You have never directly observed the surgical procedure at issue here?

A: True.

Q: You cannot point to any case with an issue like the one here where you have provided expert testimony?

A: Correct.

Q: You have not conducted any research or published any articles related to the specialized surgical procedure involved in this case?

A: That is also true.

Q: Have you given any lectures or presentations related to the specific surgical technique at issue here?

A: No.

Q: You cannot discuss any advancements or changes in the surgical technique involved in this case that have occurred in the last few years?

A: No, I cannot.

Whether a witness qualifies as an expert depends on the specifics of the case and the relevance of the proposed expert’s qualifications to the issues in dispute. For example, suppose a lawyer wanted a mechanical engineer to testify in a case involving an electrical engineering issue. The court would consider whether the mechanical engineer has qualifications relating to the electrical engineering concepts that are sufficiently relevant to the case. A mechanical engineer who has experience with electrical systems in machinery may qualify as an expert even without any formal education or degree in electrical engineering if the case involves the interaction between mechanical and electrical components in machinery, especially if the mechanical engineer has practical experience working with electrical systems as part of his or her professional career in mechanical engineering.

Admissibility Requirements under Federal Rule of Evidence 702

After a lawyer qualifies a witness by virtue of background questions, the lawyer must next address in voir dire Rule 702’s four admissibility requirements.


The first requirement is that the witness’s scientific, technical, or specialized knowledge will help the trier of fact understand the evidence or determine a fact at issue in the case. This is a relevance test. Therefore, in a medical malpractice case involving knee surgery, the lawyer could ask the following questions to establish the relevance of the proposed expert’s opinions:

Q: Are you able to offer an opinion as to whether the actions of Dr. Brody in performing knee surgery on the Plaintiff met the standard of care in the medical community?

A: Yes, I am prepared to offer such an opinion.

Basis in Sufficient Facts or Data

The proponent of the expert witness must also show that the proposed expert’s opinions are based on sufficient facts or data with questions like the following ones:

Q: Dr. Lujan, how did you form your opinion as to whether Dr. Brody’s actions deviated from the standard of care?

A: I thoroughly reviewed the Plaintiff’s medical history, pre-operative assessments, surgical notes, post-operative reports, and other relevant documentation.

Q: Can you describe the other relevant documentation you referenced?

A: I reviewed the written discovery, which consisted of the Plaintiff’s and Dr. Brody’s answers to written questions. I also reviewed both of their deposition transcripts.

An expert witness need not base opinions on personal knowledge. Many experts, particularly medical experts, base their opinions on a record review. The fact that some information in a medical file may be inadmissible hearsay is irrelevant. For example, medical records setting forth a patient history based on the patient’s description of their symptoms, statements in medical records by other health care providers, and even laboratory results, although normally inadmissible hearsay, can nonetheless provide the basis for an expert opinion if there is a sufficient foundation laid that the expert has sufficient expertise to evaluate the accuracy and reliability of the information, that the record is of the type that is normally relied on by doctors, and that it is a type of record that is typically found to be reliable.

Reliability of Principles and Methods

Reliability of the methodology for arriving at an opinion is a foundational factor in assessing the admissibility of expert testimony. The lawyer should ask the proposed expert in voir dire to describe the nature of the methodology used in forming an opinion, whether the process for arriving at the opinion offered is generally accepted, and what training and experience the proposed expert has in using the methodology to evaluate the issue in the case:

Q: Dr. Lujan, can you explain how you arrived at your opinions?

A: My methodology involved a comprehensive review of the Plaintiff’s medical records, considering established standards of care in orthopedic surgery to determine whether Dr. Brody’s actions deviated from accepted practices.

Q: Do you know whether the methodology you described is a reliable one to assess surgical procedures and outcomes?

A: It is. I have extensive experience evaluating surgical outcomes according to the process I just described. In evaluating Dr. Brody’s actions, I considered the standards set forth by the American Academy of Orthopaedic Surgeons, as well as relevant clinical practice guidelines. These standards provide a framework for assessing the appropriateness of Dr. Brody’s surgical techniques.

Q: How do you ensure the consistency and accuracy of your assessments when evaluating surgical procedures and outcomes?

A: I rely on a systematic approach to review and evaluate medical records. For example, I have a checklist of records I would expect to see in a surgical file. If I did not see any imaging studies, I would ask for those records because they are critical to forming an opinion. I draw upon my clinical experience and knowledge of established standards of care to ensure I have sufficient information to conduct an accurate evaluation.

Reliable Application of These Principles and Methods

Next, a lawyer should ask the proposed expert to explain how he or she applied the methodology to the facts of the case to arrive at an opinion:

Q: Please explain how you applied your methodology to evaluate Dr. Brody’s surgical techniques.

A: After thoroughly reviewing the Plaintiff’s medical records, I assessed each step of the surgical procedure against established standards of care in orthopedic knee surgery, evaluating the documented interventions to determine whether there were any deviations from the accepted standard of care.

Requesting Acceptance of the Expert and Eliciting Expert Opinion

Upon the completion of voir dire, the lawyer proffering a witness as an expert must request the court to accept the witness as an expert and identify the specific field of expertise in which the expert will be testifying: “Your Honor, I request that Dr. Lujan be admitted as an expert in the area of orthopedic knee surgery.”

Only after the court admits a witness as an expert may a lawyer ask the expert to provide their opinions:

Q: Do you have an opinion as to whether Dr. Brody deviated from the accepted standard of care?

A: Yes, I believe that Dr. Brody deviated significantly from the standard of care when he performed knee surgery on the Plaintiff.

Q: Please explain how Dr. Brody deviated from the standard of care.

A: Dr. Brody failed to properly position the Plaintiff’s knee during the surgical procedure, which led to improper alignment of the implant.

Q: Can you explain how Dr. Brody’s deviations from the standard of care impacted the Plaintiff’s outcome?

A: As a result of the misalignment, the Plaintiff experienced persistent pain and limited range of motion, requiring revision surgery to correct the issue.

Q: In your expert opinion, were Dr. Brody’s actions a departure from what a reasonably competent orthopedic surgeon operating on a knee would have done under similar circumstances?

A: Yes.

The qualification of an expert witness prior to eliciting his or her opinion serves as a crucial safeguard to ensure the integrity and fairness of the judicial process. It guarantees that only those with the requisite expertise are permitted to provide scientific, technical, or specialized opinion testimony, maintaining fairness and impartiality in adjudicating disputes and resolving complex legal issues. As the legal landscape evolves, the importance of robust qualification procedures for experts cannot be overstated. The legal profession must remain vigilant in maintaining high standards for the admission of expert testimony to effectively navigate the complexities of modern litigation and ensure that justice is served for all parties involved.