In substantive aspects, expert witnesses differ from other witnesses in that they are experts qualified “by knowledge, skill, experience, training, or education,” as defined under Rule 702 of the Federal Rules of Evidence. A court who has designated a witness as an expert may offer testimony if:
- 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
- the testimony is based on sufficient facts or data
- the testimony is the product of reliable principles and methods
- the expert has reliably applied the principles and methods to the facts of the case
As to substantive testimony, expert witnesses largely differ from lay witnesses, who are best defined by what they are not – experts. Rule 701 of the Federal Rules of Evidence states that if a witness is not testifying as an expert, testimony in the form of an opinion is limited to one that is:
- rationally based on the witness’s perception
- helpful to clearly understanding the witness’s testimony or to determining a fact in issue
- not based on scientific, technical, or other specialized knowledge within the scope of Rule 702
Therefore, the major difference between experts and lay witnesses is personal knowledge. Rule 602 of the Federal Rules of Evidence requires that a witness only testify if evidence sufficiently supports that the witness has personal knowledge of the facts. Rule 602 specifically exempts expert testimony from this requirement. In comparison, Rule 703 allows experts to rely upon facts and data beyond what they have personally observed. Rather, experts can consider facts that would otherwise be inadmissible, so long as experts in their particular field would reasonably rely on such information.
Retained Experts vs. Non-Retained Experts
So does this mean that all witnesses fall within the broad categories of fact witnesses and experts? Not exactly. Sometimes, an individual, who by any measurement, is an expert in their field, may testify without formally being retained by or employed by a party. Referred to as “non-retained experts,” these witnesses check all the boxes of an expert. They possess the requisite knowledge, skill, education, etc., but they are testifying to facts that they personally observed, as opposed to experts who are typically evaluating a case after the event or fact at issue took place. Most often seen when treating physicians of an injured plaintiff, these witnesses are not offering opinions beyond the purview of a fact witness.
This means that their testimony is limited in ways in which expert testimony is not. However, whenever any person of certain credentials is put forth before the jury, the implications of their title can affect their credibility. As such, there are certain rules surrounding the testimony of non-retained expert witnesses that should be considered.
Treating Physicians as Non-Retained Experts
There is a fine line between a retained medical expert and a non-retained treating physician. Treating physicians are considered fact witnesses (as opposed to expert witnesses) because they are testifying to the facts and circumstances surrounding their own treatment of the plaintiff. Like a fact witness, a treating physician will only testify to their observations concerning their own personal diagnosis, examination, or treatment of the patient. Likewise, the treating physician will only testify to procedures personally conducted and will only rely on notes and reports that were personally created in the ordinary course of their duties as the plaintiff’s physician.
Unlike witnesses designated as experts under Rule 702, treating physicians are not rendering a medical opinion as to causation or the defendant’s contribution, if any, to the plaintiff’s injury. For example, a physician that treated a patient after a car accident can testify to the injuries sustained, such as a broken bone, and the necessary procedures and treatments. A medical expert (or other experts, such as an accident reconstructionist) would often be needed to establish that the broken bone was an injury that, in fact, resulted from the defendant driver’s negligent conduct.
That being said, treating physicians are referred to as non-retained experts (as opposed to mere fact witnesses) for a reason. Though not designated an expert by the applicable legal standards, a treating physician or another professional can still be considered an expert in the more substantive, colloquial sense, i.e., they have the requisite skill, knowledge, or education and possess scientific or other specialized knowledge that could help the jury understand an issue of fact. So although a non-retained expert’s testimony is limited to that of personal observation, they are not considered a lay witness. As such, it is important that a non-retained expert testifies accordingly, since slipping into the retained expert role and giving opinions not based on their own treatment, can have unintended consequences.
Because there are different evidentiary standards for retained experts and non-retained experts (or fact witnesses), with the latter having a lower standard for admissibility, many federal courts have rejected attempts wherein treating physicians or other non-retained experts impermissibly offer expert opinion.
Disclosure Requirements of Non-Retained Experts
Aside from the implications that the “expert” label has on a jury, one of the most critical reasons why experts are distinguished from non-retained, fact witnesses is due to the different disclosure rules that apply. Under Rule 26(a)(2)(A) of the Federal Rules of Civil Procedure, all parties must disclose the identity of any expert witnesses it may use at trial to present evidence under the Federal Rules of Evidence that govern expert admissibility. Rule 26 (a)(2)(B) of the Federal Rules of Civil Procedure defines a retained expert as one who is “retained or specially employed to provide expert testimony in the case or one whose duties as the party’s employee regularly involve giving expert testimony,” and in which case, the Rule requires that the witness must provide a written report to opposing counsel.
Pursuant to the Rule, the report must contain a summary of the expert’s opinion and its basis; the facts or data on which the expert relied; any exhibits that will be used; the expert’s qualifications (including a list of all publications authored in the past ten years); a list of cases for which the expert testified in the past four years; and the expert’s compensation for the instant case.
In contrast, witnesses who do not fall under Rule 26(a)(2)(B) as “retained or specially employed to provide expert testimony,” but are still expected to present scientific evidence, need not provide a written report. Under Rule 26(a)(2)(C), only the subject matter and a summary of facts and opinions to which such a witness is expected to testify need be disclosed. Therefore, non-retained treating physicians may testify to scientific or other specialized matters but are exempt from the more stringent written report requirement because they are not “retained or specially employed to provide expert testimony.” However, these more liberal disclosure standards operate the same as the lower evidentiary burden of non-retained experts – the witness must keep their opinions limited to their own participation in the events of the case, lest they be precluded.
While treating physicians are perhaps the most frequent example of a non-retained expert, there are a number of professionals (law enforcement, lawyers, accountants, etc.) that may be needed to testify in a case due to their contemporaneous involvement in the incident at issue. Though these individuals may possess a skill level that would enable them to render expert opinions under the law, if they are not designated as expert witnesses, it is best to proceed cautiously, with due consideration to the different evidentiary standards.