Expert Witness


Members of the medical profession may be asked to testify sometime during their career. It is in the best interest of the legal and medical professions if this testimony, in either a civil or criminal case, is scientifically sound and provided by an unbiased expert witness. Medical professionals, as members of the medical community, patient advocates, and private citizens, have a professional and ethical responsibility to assist with the civil and criminal judicial processes.[1][1][2]

Evidence-based and experience-based opinions from medical professionals in legal cases have become increasingly important and common. Many professional medical societies (American College of Obstetrics and Gynecology, American College of Emergency Physicians, American Academy of Pediatrics, American Society of General Surgeons, American Association of Neurologic Surgeons,  American Academy of Orthopedic Surgeons, American Academy of Ophthalmology, American College of Cardiology, and American College of Radiology) have addressed the issue with recommendations or guidelines.

Legal Concepts

Medical Malpractice

Medical malpractice law is based on tort and contract law, and it is commonly understood as liabilities that arise from the delivery of medical care.  These liabilities may be based on negligence, insufficiently informed consent, intentional misconduct, breach of a contract, defamation, divulgence of confidential information, or failure to prevent foreseeable injuries to third parties.[3][4]

Of all of the potential liabilities in medical malpractice, medical negligence is the most common.  Medical negligence requires that the plaintiff establish the following elements:

  1. The existence of the physician’s duty to the plaintive, usually based on the existence of a physician-patient relationship.
  2. The applicable standard of care and its violation.
  3. Damages, a compensable injury.
  4. A causal connection between the violation of the standard of care in the injury.

Standard of Care

In medical malpractice cases, the defendant’s behavior is compared to the standard of care for that specific situation. The standard of care is most commonly defined as, “that reasonable and ordinary care, skill, and diligence as physicians and surgeons in good standing in the same neighborhood, the same general line of practice, ordinarily have been exercising in like cases.” Nowadays, with the establishment of national boards and greater standardization of practice, there is less local variability. The exception is access to care and health care facilities in underserved or rural areas.[5]

The question of whether there was a deviation from the standard of care, is often the most crucial decision of the expert witness in medical liability cases. If it is determined that a deviation from the standard of care has occurred, a secondary role for the expert witness may be to provide an opinion regarding whether the deviation of the standard of care could have been the cause of the patient’s alleged injury.

Medical Errors Compared to Medical Negligence

There are several possible outcomes from a medical intervention; the condition improves, the condition worsens, and the condition remains unchanged. A deterioration in the patient’s condition does not necessarily indicate medical negligence. The three above outcomes are possible with appropriate care and treatment. Medical negligence cannot be determined solely from an unexpected result, an unacceptable result, a failure to cure, a failure to recover or any other situation which might indicate a lack of success of the intervention or care.

Burden of Proof

The burden of proof is different in civil cases than in criminal cases.  In civil cases, the plaintiff must convince the jury of its position with a preponderance of the evidence. A preponderance of the evidence means at least 51%. Therefore, the jurors in a medical negligence case must be convinced that the argument and evidence provided by the plaintiff are more plausible as the proximate cause of the alleged injury than the argument and evidence provided by the defendant.


In the United States judicial system, the expert witness has an essential function in determining medical negligence. The role of the expert witness testimony in medical malpractice cases is three-fold. The expert witness is called on to establish the standard of care applicable to that specific case. The expert is then asked to provide an opinion regarding any deviation from the standard of care. Lastly, if it is determined that there was a deviation from the standard of care, the expert witness may be asked to offer an opinion as to whether that deviation from the standard of care could have resulted in the patient’s alleged injury.[6][7][8]

Processes of Expert Witness

The involvement of the expert witness in medical malpractice cases can take many different forms. The expert witness may be asked to evaluate the merits of a claim before legal action is filed. The expert witness may be tasked to review the medical records, provide a written opinion regarding the standard of care and any deviation from the standard of care. If the case continues, the expert will most likely be deposed. During a deposition, the expert witness provides recorded testimony, under oath, to the questions of attorneys from both sides. If the case goes to court, the expert witness will be required to provide testimony, under oath, to the judge or jury.

The judge and jury rely on the expert witness to clarify the medical standards. Therefore the testimony should be clear, coherent, and consistent with the standard of care applicable at the time of the incident.[9]

Issues of Concern

The testimony of the expert witness is often a crucial component of a medical malpractice case.  Therefore, the testimony must be objective, accurate, reliable, and an appropriate analysis of the medical record as it relates to the standard of care. One of the most significant concerns among the legal community regarding expert witnesses is that not all experts provide testimony that is ethical and supported by scientific or medical evidence.

There are some examples of inappropriate testimony provided by expert witnesses and the effect of that testimony on the outcome of the case. As a result of these types of cases, when determining whether the testimony of the expert should be admissible in court, judges should consider the following: (1) whether the expert’s opinion has been peer-reviewed, (2) whether the expert can and has been tested, (3) the known or potential error rate of the theory; and (4) the general acceptance of the theory in the relevant scientific community.

The court determines the admissibility of expert medical testimony. Daubert is still frequently cited by trial courts when ruling on a motion to preclude expert testimony.[10] Physicians may be asked to testify about patients whom they have not taken a medical history nor examined personally. Nevertheless, they are expected to make estimates about causation, risk of injury, or surmise future injuries. They may even need to assess the medical records of a deceased litigant.

To ensure the highest quality and appropriate expert witness testimony, some professional medical societies have published recommendations or guidelines for expert witnesses in these specific medical specialties.

Examples of expert witness guidelines are provided below.

Clinical Significance

The expert witness plays an important role as an educator for the attorneys, the judge and the jury. The expert must be able to review the specific case and recognize which aspects of the care and interventions, provided or not provided, are clinically significant. This testimony enables the attorneys to direct their arguments better and discuss only what is relevant. Also, the expert should be able to “translate” the scientific, medical terminology so that someone without any medical training can understand the clinically significant issues of a case. By providing education to the judge and jury, the expert witness assists them in reaching a more appropriate conclusion regarding the facts of the case than they would have without the expert’s testimony.

Other Issues

Examples of Society Recommendations

Expert Witness Recommendations from the American Academy of Pediatrics (AAP)

Advocacy and Education

The AAP believes that the establishment of certain minimal qualifications for physicians serving as expert witnesses will improve the quality of testimony and promote just and equitable verdicts. Therefore, the AAP supports efforts to:

  1. Implement the recommendations of this statement through legislative or regulatory reform of expert witness testimony (e.g., establish minimal qualifications for expert witnesses in medical negligence); and
  2. Educate pediatricians (during residency training and through continuing medical education) to provide them with the skills and knowledge base needed to provide objective, scientific, and ethical expert witness testimony in legal proceedings involving alleged medical negligence.

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.

  1. Physician expert witnesses must hold a current, valid, and unrestricted medical license in the state in which they practice medicine.
  2. Physician expert witnesses must be certified by the relevant board recognized by the American Board of Medical Specialties or a board recognized by the American Osteopathic Association.
  3. 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.
  4. 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 (for example, development of vaccines, cloning, DNA testing) 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 a thorough, fair, objective, and impartial review of medical facts. To meet that obligation, physicians agreeing to testify as experts in medical negligence cases should conduct themselves as follows:

  1. 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.
  2. 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.
  3. Relevant information should not be excluded for any reason and certainly not to create a perspective favoring the plaintiff or the defendant.
  4. 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. Becoming schooled on a medical standard after accepting a case may lead to a biased understanding of the issue. A physician unfamiliar with the medical standards would not meet the recommended qualifications of an expert.

  1. 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.
  2. The testimony presented should reflect accepted standards within the specialty or area of practice about which the expert witness is testifying, including those held by a significant minority.
  3. When a variety of acceptable treatment modalities exist, this should be stated candidly and clearly.
  4. Expert witness testimony should not condemn performance that falls within generally accepted practice standards or condones performance that 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:

  1. Base distinctions made between medical malpractice and medical maloccurrence on science, not on unique theories of causation;
  2. know that transcripts of depositions and courtroom testimony are public records and may be reviewed by audiences outside of the courtroom; and
  3. be willing to submit transcripts of depositions and courtroom testimony for peer review.

Ethical Business Practices

The business practices (e.g., 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.

  1. Contractual agreements between physician expert witnesses and attorneys should be structured in a way that promotes fairness, accuracy, completeness, and objectivity.
  2. Compensation for expert witness testimony should be reasonable and commensurate with the time and effort involved.
  3. Physicians should not enter into contracts in which the fees for expert witness testimony are disproportionately high relative to the time and effort involved.
  4. Physicians should not enter into contracts in which the compensation for expert witness testimony is contingent on the outcome of the case.

Expert Witness Guidelines for the Specialty of Emergency Medicine from the American College of Emergency Medicine 

To qualify as an expert witness in the specialty of emergency medicine, a physician shall:

  • Be currently licensed in a state, territory, or area constituting legal jurisdiction of the United States as a doctor of medicine or osteopathic medicine;
  • be certified by a recognized certifying body in emergency medicine;
  • have been in the active clinical practice of emergency medicine for at least three years (exclusive of training) immediately preceding the date of the occurrence giving rise to the case. A physician serving as an expert witness who is not currently engaged in the clinical practice of emergency medicine shall be considered to have met this requirement if he or she was so engaged during the three years immediately preceding the date of the occurrence giving rise to the case.

Abide by the Following Guidelines

  • The expert witness should possess current experience and ongoing knowledge in the area in which he or she is asked to testify.
  • The expert witness should not provide expert medical testimony that is false, misleading, or without medical foundation.2 The key to this process is a thorough review of available and appropriate medical records and contemporaneous literature concerning the case being examined.
  • A medical expert’s opinion should reflect the state of medical knowledge at the time of the event giving rise to the case.
  • The expert witness should review the medical facts in a thorough, fair, and objective manner and should not exclude any relevant information to create a view favoring either the plaintiff or the defendant.
  • Expert witnesses should be chosen on the basis of their experience in the area in which they are providing testimony, and not on the basis of offices or positions held in medical specialty societies unless such positions are material to the expertise of the witness.
  • An emergency physician should not engage in advertising or solicit employment as an expert witness where such advertising or solicitation contains false or deceptive representations about the physician’s qualifications, experience, titles, or background.
  • The expert witness should be willing to submit the transcripts of depositions and testimony to peer review.
  • An expert witness should never accept any compensation arrangement that is contingent on the outcome of litigation.
  • Misconduct as an expert, including the provision of false, fraudulent, or misleading testimony, may expose the physician to disciplinary action.
  • Be not only familiar with the local state law, regulations, and practice of emergency medicine but also strictly adhere to the state-specific definitions of negligence.

Enhancing Healthcare Team Outcomes

The medical records are the responsibility of the health care team of nurses, technicians, paramedical staff, medical residents, consultants, and attending physicians or surgeons. Medical documentation must be accurate, complete, and timely. 

Article Details

Article Author

Yasmyne Ronquillo

Article Author

Kenneth J. Robinson

Article Editor:

Patricia P. Nouhan


6/27/2022 11:44:30 PM



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