Expert Testimony: Pointers and Pitfalls on Being an Expert Witness

Dr Andrew has been an expert witness in dozens of cases. In this article he describes the role of the expert before and at the trial.

Expert Witness Dr Thomas Andrew

The Role of the Expert

  • Corroboration of theory of the case as offered to the trier of fact by the attorneys
  • The expert witness may offer opinions based on their own work in the case or on facts in evidence
  • May provide the leverage for settlement without trial


Prior to the start of the trial the expert witness will be required to prepare in a variety of ways.

  • Reports provided to the retaining attorney for presentation to the court and opposing counsel
  • Preparation of visual aids to be used during trail to aid the jury in understanding evidence and opinions.
  • Review of all available relevant material
  • Review of opposing expert’s opinion
  • Pre-trial conference with the attorney who has retained your services. This will be routinely questioned in an accusatory manner by opposing counsel, but is not only perfectly appropriate, but essential.

Payment as an Expert Witness

As an expert witness it is expected that your testimony will command a fee commensurate with your relevant expertise and the amount of time that you will spend on the case.

A fee schedule detailing how much you are to be paid, and for what will be necessary, you cannot accept fees that are contingent on the outcome of the trial.

As with the pre-trial conference you will likely be questioned about your fees on the stand. Do not be defensive or vague. Everyone there is being paid, but you are the only one who is compelled to disclose how much. Those are the rules. Always remember: 1) you are not “being paid for your testimony (or your opinion)” You are being paid for the time you committed as an expert in the field to the case at hand, and 2) whatever your rate, it will made to appear exorbitant. Just answer the questions and keep the ball rolling.

Credibility/Courtroom Demeanor

Attitude is important. Are you an objective scientist or hired gun? The latter is characterized by irresponsible testimony for example:

  • Testimony outside your Qualifications
  • Unique theories of causation
  • Unique interpretations
  • Assertion of nonexistent findings
  • Misquotation of the relevant literature
  • False statements
  • Deliberate omissions

Who is an “expert?”

Several court cases as well as sets of guidelines from various organizations provide the definition of an expert. These include the following:

Daubert vs. Merrill Dow

Daubert v. Merrell Dow Pharmaceuticals, 509 U.S. 579 (1993) is a United States Supreme Court case determining the standard for admitting expert testimony in federal courts.

Under Daubert:

  • The judge is the gatekeeper, assuring that scientific expert testimony truly proceeds from “scientific knowledge.”
  • Relevance and reliability: This requires the trial judge to ensure that the expert’s testimony is “relevant to the task at hand” and that it rests “on a reliable foundation.”
  • The Judge must find it more likely than not that the expert’s methods are reliable and reliably applied to the facts at hand.
  • Scientific knowledge = scientific method/methodology: A conclusion will qualify as scientific knowledge if the proponent can demonstrate that it is the product of sound “scientific methodology”/derived from the scientific method. This is a grey area when it comes to forensic pathology as medicine is both art and science, but it is a bridge all experts must negotiate.
  • The Court defined “scientific methodology” as the process of formulating hypotheses and then conducting experiments to prove or falsify the hypothesis.
American Academy of Pediatrics Expert Witness Guidelines

Relevant Qualifications

  • Physicians should limit their participation as medical experts to cases in which they have genuine expertise. The following qualifications must be met (and verified) to demonstrate relevant education, certification, and experience.
    • Physician expert witnesses must hold a current, valid, and unrestricted medical license in the state in which they practice medicine.
    • Physician expert witnesses must be certified by the relevant the board recognized by the American Board of Medical Specialties or a board recognized by the American Osteopathic Association.
    • Physician expert witnesses must be actively engaged in clinical practice in the medical specialty or area of medicine about which they testify including knowledge of or experience in performing the skills and practices at issue to the lawsuit.
  • It may be appropriate for an expert in the area of research that is complicated to be asked to explain the nature of the research to the jury (i.e., development of vaccines, cloning, DNA testing, etc.) that may be purely educational and not relate to the clinical care provided by the defendant.

Unbiased and Complete Testimony

  • Physicians serving as experts in medical negligence actions should take all necessary steps to provide thorough, fair, objective, and impartial review of medical facts.
  • Regardless of the source of the request for testimony (plaintiff or defendant physician), expert witnesses should lend their knowledge, experience, and best judgment to all relevant facts of the case.
  • Expert witnesses should take necessary steps to ensure that they have access to all documents used to establish the facts of the case and the circumstances surrounding the occurrence.
  • Relevant information should not be excluded for any reason and certainly not to create a perspective favoring the plaintiff or the defendant.
  • The expert witness’s opinion should be fair and objective. The expert witness should be comfortable with his or her testimony regardless of whether it is to be used by the plaintiff or defendant.

Standards of Care

  • The physician expert witness should be familiar with the medical standards at issue before accepting a case.
  • Before testifying, the physician expert witness should review and understand the current concepts and practices related to that standard as well as the concepts and practices related to that standard at the time of the occurrence that led to the lawsuit.
  • The testimony presented should reflect generally accepted standards within the specialty or area of practice about which the expert witness is testifying, including those held by a significant minority.
  • When a variety of acceptable treatment modalities exist, this should be stated candidly and clearly.
  • Expert witness testimony should not condemn performance that clearly falls within generally accepted practice standards or condone performance that clearly falls outside accepted practice standards.

Assessing Breach of Care and Proximate Cause

  • Physician expert witnesses must exercise care in assessing the relationship between the breach in the standard of care and the patient’s condition, because deviation from a practice standard may not cause the patient outcome at issue. Thus, medical expert witnesses should:
  • Base distinctions made between medical malpractice and medical maloccurrence on science, not on unique theories of causation;
  • Know that transcripts of depositions and courtroom testimony are public records and may be reviewed by audiences outside of the courtroom; and
  • Be willing to submit transcripts of depositions and courtroom testimony for peer review.

Ethical Business Practices

  • The business practices (eg, marketing, contractual agreements, and payment for services) associated with the provision of expert witness testimony must be conducive to remaining nonpartisan and objective throughout the legal proceedings.
  • Contractual agreements between physician expert witnesses and attorneys should be structured in a way that promotes fairness, accuracy, completeness, and objectivity.
  • Compensation for expert witness testimony should be reasonable and commensurate with the time and effort involved.
  • Physicians should not enter into contracts in which the fees for expert witness testimony are disproportionately high relative to the time and effort involved.
  • Physicians should not enter into contracts in which the compensation for expert witness testimony is contingent on the outcome of the case.
The Ikarian Reefer (

The principle duties and responsibilities of an expert witness have been summarized by Mr. Justice Cresswell in National Justice Compania Naviera SA v Prudential Assurance Company Ltd. , (also known as the “Ikarian Reefer” case).

In the Ikarian Reefer case Mr Justice Cresswell said that he believed that a misunderstanding on the part of certain of the expert witnesses in the case as to their duties and responsibilities contributed to the length of the court proceedings. It was for these reasons that during his judgement he set out the following:

  • Expert evidence presented to the court should be the independent product of the expert uninfluenced as to form or content by the exigencies of litigation.
  • An expert witness should provide independent assistance to the court by way of objective unbiased opinion in relation to matters within his expertise. An expert witness should never assume the role of an advocate.
  • An expert witness should state the facts or assumptions upon which his opinion is based. He should not omit to consider material facts which could detract from his concluded opinion.
  • An expert witness should make it clear when a particular question or issue falls outside his expertise.
  • If an expert’s opinion is not properly researched because he considers that insufficient data are available, then this must be stated with an indication that the opinion is no more than provisional.
  • If, after exchange of reports, an expert witness changes his view on a material matter such a change of view should be communicated (through legal representatives) to the other side without delay and when appropriate to the court.
  • Where expert evidence refers to photographs, plans, calculations, analyses, measurements, survey reports or other similar documents, these must be provided to the opposite party at the same time as the exchange of reports.


The testimony presented and the manner in which it is presented will be dependent on the circumstances of the court proceedings. Is this a(n)

  • inquest?
  • Deposition?
  • Grand jury?
  • Hearing?
    • Pre-trial?
    • Evidentiary/Daubert?
    • Hearing on a motion during trial?
  • Trial?
    • Criminal?
    • Civil?

Stages of Testimony

Direct examination – generally open-ended questions fashioned for the expert to fully explain his/her opinion(s) and he basis for same

Cross examination – generally short, pointed questions fashioned to pick at perceived shortcomings of the expert’s technique, methodology, competence and probative value of any proffered opinions. These are often reduced to a “yes” or “no” format that can mislead a jury. It is not the expert’s role to point this out. This may come in the form of an objection, or be clarified during . . .

Re-direct examination – it is at this time the attorney who conducted the expert’s direct examination can clarify any misleading questions or allow the expert to expand on an issue shut down because of the nature of cross-examination.

Re-cross and re-direct may continue as long as the presiding judge permits.

Lastly, stay calm, even in the face of denigrating questions and ad hominem tactics. Be polite, and do not leave the stand until dismissed by the judge. Providing expert testimony is not for the faint of heart but can be very rewarding. An understanding of one’s role, how the proceeding works and following a few simple rules of conduct can make he ordeal much more palatable.

Recommended reading: The Role of the Expert Witness in a Court Trial, Benjamin J, Cantor, J.D., Civil Evidence Photography Seminars, Belmont, MA, 1997