Medical Expert Witnesses and Their Role in Modern Litigation

Stephen Gomez

Written by
— Updated on June 11, 2020

Medical Expert Witnesses

Medical expert witnesses have become an integral part of modern litigation. Experts in the medical field are brought to discuss different elements of a case. This can range from items related to the design of medical devices, to the effects of a given pharmaceutical product or procedure. A medical expert witness couples their training and certification with their relevant experience, providing expert opinion on the facts of a case. The expert’s role, however, has developed over time, changing and evolving with the legal landscape. This process has continued, with expert witnesses creating a niche that is unique to American jurisprudence. Because of this, and this shift, it is important to trace the medical expert witness’s changing role, and the position they occupy today.

II. The Pre-Frye History of the Medical Expert Witness
medical expert witnesses 1900

In many cases, the standard for a medical expert witness began with the Frye decision, and the facts contained therein.[1] There are a number of items, however, that pre-date the Frye decision. These directly affect the finding and contribution of medical expert witnesses in a modern case. Consider this quote, from Lee M. Friedman, in an article from Yale Law Journal in 1910,” Almost from the beginning of the use of expert testimony in our courts a conflict has been waged over its real probative value.”[2]

At the turn of the (previous) century, the legal community extensively discussed the question of an expert’s role in litigation. Justice Learned Hand wrote on the topic, tracing the expert’s role back to its English roots.[3] In his opening lines, Justice Learned Hand stated,” No one will deny that the law should in some way effectively use expert knowledge wherever it will aid in settling disputes. The only question is as to how it can do so best.”[4]

This notion was becoming increasingly important because expert witness usage was growing. For example, as Friedman pointed out, in the early part of the 1900’s, the New York State Bar Association appointed a committee to consider any issues that may arise because of the use of medical expert witnesses.[5] In their list detailing the issues facing the courts, with regards to the use of a medical expert witness, the first item was, “Want of satisfactory standards of expertness with its result of inviting the testimony of charlatans.”[6]

The Bar Association’s committee set forth other issues to address, but the primary concern dealt with the status of an expert and how one could be designated as such. For medical experts, today, this is a critical determination. Prior to common law (and later statutory law) establishing guidelines to judge relevant expertise, standards varied widely between jurisdictions.

Some states judged cases as they came about, and others dealt with the issue with different statutes. For example, Michigan passed a law limiting expert witnesses in non-homicide cases, and Rhode Island passed a bill which allowed for the court to appoint an expert to speak on the issue at hand.[7] Because of this lack of uniformity, experts’ opinions were given different weights by judges (in their instructions to the juries), varying from, “merely calling to their [the jury’s] attention the fact that the experts are called by contestants, to [such] extreme expressions of personal opinion.”[8] Judges were given discretion to allow and disallow expert testimony, but there were relatively few guidelines establishing what a judge should consider.

This variability created a sense of uncertainty, particularly around scientific measures. The dissatisfaction grew, and it was not until the Frye decision that the country identified a specific standard that would serve as a widespread model.[9]

III. From Frye…

By 1923, there wasn’t a standard rule for evaluating an expert. That changed with the Frye decision. In the case, a criminal defendant was appealing a decision based on the results of a polygraph test. This machine measured changes in the systolic blood pressure and the operator of the machine would then correlate these changes with the defendant’s truthfulness.[10] The court ruled against the admittance of an expert’s testimony regarding the polygraph’s results. Stating a consensus that the technology was too new, and its validity and reliability had not been established. Furthermore, the court established the Frye standard by stating:

Just when a scientific principle or discovery crosses the line between the experimental and demonstrable stages is difficult to define. The evidential force of this principle will be recognized somewhere in this twilight zone. While courts will go a long way in admitting expert testimony deduced from a well-recognized scientific principle or discovery, the thing from which the deduction is made must be sufficiently established to have gained general acceptance in the particular field in which it belongs.[11]

The key component of the Frye standard was the determination that the scientific principle must be “sufficiently established to have gained general acceptance.” This rule placed a burden on the judge to determine if the larger, relevant scientific community accepted the findings of the expert witness.

This standard was roughly in place for around seventy years, before it was replaced by the Daubert standard. The Frye standard, while giving some guidelines for judges to consider (which was an improvement over the amorphous standard that governed medical expert witnesses prior to its inception), there were some issues that emerged as medical developments occurred during the century. Frye’s “general acceptability” standard excluded many new discoveries that did not have time to become generally accepted in the relevant scientific community.[12] Additionally, general acceptability was hard to establish in highly specialized areas of inquiry where there may only be a few experts. It was also problematic if the plaintiff was arguing that the conventional wisdom (thus, that which is “generally accepted”) was not true. Lastly, the Frye standard, “proved difficult to administer, encouraging judges to allow broad latitude for the admission of questionable evidence.”[13]

III. …To Daubert
medical expert witnesses 1975

Two actions limited the Frye standard’s effect in litigation. First, Congress passed the Federal Rules of Evidence in 1975, which outlined a new standard to consider expert witness testimony. Specifically, Rule 702 stated:

A witness who is qualified as an expert by knowledge, skill, experience, training, or education may testify in the form of an opinion or otherwise if:

(a) the expert’s scientific, technical, or other specialized knowledge will help the trier of fact to understand the evidence or to determine a fact in issue;

(b) the testimony is based on sufficient facts or data;

(c) the testimony is the product of reliable principles and methods; and

(d) the expert has reliably applied the principles and methods to the facts of the case.[14]

This established a standard which provided the judge as a gatekeeper for the admittance of the evidence, and allowed her/him to consider the totality of the circumstances in deciding whether to admit an expert’s testimony. It is important to note that the FRE were simply a guideline, and did not have applicability to actual proceedings until states adopted the standard through common law or statute, and did not apply to federal courts until a 1992 Supreme Court case.

In a landmark decision, the Court upheld the requirement that the trier of fact would be satisfied only if the opinion had “a valid scientific connection to the pertinent inquiry.”[15] This case involved the plaintiff bringing suit against a pharmaceutical company for birth defects allegedly caused by the drug, Bendectin. While the scientific community had not yet reached a consensus on the effects of the drug (or general acceptability), the plaintiff sought to introduce evidence from expert witnesses that linked the birth defects to the drug. The lower courts denied admittance of the evidence, but the Supreme Court reversed, stating that the judge had a “gatekeeping” function in allowing evidence. Relevant factors could include:

1. whether the expert’s theory can be or has been tested;

2. whether the theory has been subject to peer review and publication;

3. the known or potential rate of error of a technique or theory when applied; or

4. the existence and maintenance of standards and controls.[16]

The Daubert standard has come to replace the Frye standard, the dominant test throughout the country. Currently, only ten states continue to adhere to the Frye standard, or some derivation. These states include California, Illinois, Kansas, Maryland, Minnesota, New Jersey, New York, Pennsylvania, and Washington. Recently, Florida discontinued its adherence to Frye on July 1, 2013. The majority of states have adopted the Daubert standard, though several states refuse to explicitly adopt either Frye or Daubert, but choose to apply similar standards that acknowledge Daubert.[17]

IV. The Modern, Medical Expert Witness
medical expert witnesses modern dayThis historical development has brought us to the modern era, and the role that medical expert witnesses currently fill in litigation. Simply put, expert witnesses are essential in modern lawsuits. The numbers for expert witness are growing.

In a study of over 500 trials, experts were witnesses in 86% of hearings, with an average of 3.3 experts per trial.[18] When looking at the different medical cases that use these experts, however, the specific subjects and items that they discuss are important to consider. To highlight this point, consider a recent case regarding foot drop after a total hip replacement procedure. In the case, the plaintiff had a total left hip replacement, and as a result of the procedure, suffered foot drop. An injury to the sciatic nerve is typically the cause and a medical expert witness needs to discuss that.

Analyzing this case, there are a number of layers that highlight the difficulties in modern, medical litigation. The procedure, itself, involves a complex device (a hip implant), which has been subject to thousands of lawsuits. As such, the medical witness should be familiar with the medical device, the risks inherent in a procedure involving said device, and ultimately, any other information pertinent to the jury. Additionally, the installation of the device, and the approach chosen, may have added risks. Was the physician correct in the approach he/she took even if a hip implant device is chosen to be installed?

This can come into play in medical device cases because usually, new devices come out on a yearly basis. Consequently, the relevant medical community may not have time to reach a consensus on the “best” way to perform a procedure. Lastly, the postoperative and subsequent measures will need to be analyzed. Did improper, follow-up procedures exacerbate the harm allegedly caused by the defendant-physician?

In the hip replacement case, consider all of the different elements that the medical expert witness (likely an orthopedic surgery expert witness), has to be familiar with in order to effectively comment as an expert. He/she may not have to testify on every element on the list, but be familiar with each step of the process to be accurately prepared for different issues that may arise during litigation and cross-examination by opposing counsel. Overall, for many cases, there are medical, regulatory, legal, procedural, engineering, and administrative concerns that the expert may have to address. Summarily, combining these complex, multi-layered ideas, and distilling them into manageable parts for the jury is one of the challenges of acting as a medical expert witness.

V. More Stages of Treatment means More Experts
With the specialization of medicine, treatment frequently involves multiple practitioners at different stages of treatment. Subsequently, in litigation, many cases require more than one medical expert witness. In another recent lawsuit involving the effects of amiodarone, a drug used to treat patients with heart issues, the case involved a cardiologist, a pulmonologist, and a radiologist. Subsequently, it is conceivable that during the trial a cardiology expert witness, a pulmonology expert witness and a radiology expert witness will testify.

With matters involving multiple practitioners, the issues discussed become increasingly complicated, especially in cases where medical experts witnesses are used more frequently. Over twenty-six expert witnesses testified in a recent DePuy Hip litigation case.[19] While this case was one of the first lawsuits to rule on the company’s liability for an allegedly defective design of their hip implant, and consequently increased the importance of the case to act as a bellwether for future actions, it illustrates the expert witness usage in today’s litigation. Subsequently, mass torts involving Stryker, GranuFlo and NaturaLyte, and transvaginal mesh implants continue their litigations. Therefore, attorneys need to be cognizant of the different expert witnesses that may discuss the different medical items associated with the subject of litigation.

Legislatively, states are putting in place measures to ensure that expert witnesses are a critical component of the legal process. States may require plaintiffs to supplement their complaint with an affidavit by a medical practitioner before a defendant-physician can properly file a suit. Other measures enacted by legislatures include requiring the medical expert witness to be in good standing. Usually this means board certified in a specialty similar to that of the defendant-physician, and some states even require that the medical expert witness still be actively practicing in order to be qualified as an expert.

These measures illustrate legislatures’ attempts to standardize the role of the medical expert witness. To conclude, while changes with their roles continue to move in conjunction with changes in the medical and legal landscapes, their importance in litigation is likely to grow and they will continue to be an impactful component of the process.


[1] Frye v. United States, 293 F. 1013, 1014 (App. D.C. Dec. 03, 1923).

[2] Lee M. Friedman, Expert Testimony, Its Abuse and Reformation, 19 Yale L. J. 247 (1910).

[3] Learned Hand, Historical and Practical Considerations Regarding Expert Testimony, 15 Harv. L. Rev. 40,  41-58 (1901).

[4] Id.

[5] See Friedman.

[6] Id.

[7] Id.

[8] Id.

[9] Frye v. United States, 293 F. 1013, 1014 (App. D.C. Dec. 03, 1923).


[11] See Frye.


[13] Id.

[14] Pub. L. 93–595, §1, Jan. 2, 1975.

[15] Daubert v. Merrell Dow Pharm., Inc., 509 U.S. 579 (1993)

[16] Id.


[18] Edward J. Imwinkelried, Rationalization and Limitation: The Use of Learned Treatises to Impeach Opposing Expert Witnesses, 36 Vt. L. Rev. 63, 64-80 (2011). Citing: Samuel R. Gross, Expert Evidence, 1991 Wis. L. Rev. 1113, 1119 (1991).

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