Unlike other testifying experts in litigation, hybrid witnesses give both fact and opinion testimony based on their first-hand knowledge of relevant facts as well as their training and experience in a particular field. Hybrid witnesses can be invaluable in bolstering a party's case, but they are subject to certain limitations and their use can raise unique legal and tactical issues. Before designating an individual as a hybrid witness, or challenging an opposing party's hybrid witness, counsel must understand the parameters of hybrid witness testimony and the implications of using hybrid witnesses at each phase of a litigation.

Testimony from both fact and expert witnesses is often necessary to establish a claim or defense in litigation. There are three types of testifying expert witnesses:

  • Experts specially retained to provide expert testimony in a case (sometimes referred to as retained experts).
  • Parties' employees whose duties regularly involve giving expert testimony.
  • Hybrid witnesses (sometimes referred to as nonretained experts).

Hybrid witnesses are fact witnesses with first-hand knowledge of the occurrences at issue in a lawsuit who also have the requisite training, skill, education, and experience that qualify them to provide expert testimony in the case under Federal Rules of Evidence (FRE) 702, 703, and 705 (see Ford v. NCL Bahamas Ltd., 2019 WL 3937127, at *2, *6-8 (S.D. Fla. June 4, 2019)). Hybrid witnesses can use their knowledge and experience in a particular field to interpret the facts they observed, give opinion testimony, and form conclusions about those facts. They are often professionals, such as engineers, physicians, and accountants. A typical example of a hybrid witness is a physician who diagnosed and treated a patient for personal injuries sustained in an accident and later offers expert testimony in a resulting personal injury lawsuit based on the physician's diagnosis and treatment of the patient-plaintiff.

This article provides guidance for counsel on how to navigate a case involving hybrid witnesses from discovery through trial. It addresses:

  • The benefits of using hybrid witnesses.
  • The scope and limits of hybrid witness testimony.
  • Disclosure requirements under the Federal Rules of Civil Procedure (FRCP) that apply to hybrid witnesses.
  • Privilege issues specific to hybrid witnesses.
  • Considerations for taking or defending depositions of hybrid witnesses.
  • The use of Daubert motions to exclude hybrid witness testimony at trial.
  • How to prepare a hybrid witness for trial or challenge the opposing party's hybrid witness testimony.


Hybrid witnesses can offer several advantages over other testifying experts, including:

  • Direct knowledge of the relevant information. Compared to retained experts, hybrid witnesses have more in-depth knowledge of the client's products, services, and inner workings. For example, a developer for a company may have knowledge about the company's product lines or other information about the company that an outside expert may not be able to access or learn. Given their personal involvement in the underlying circumstances of the case, hybrid witnesses may have a better understanding of what information is important to convey to a jury and how to credibly respond to an unexpected question or area of inquiry by opposing counsel.
  • Cost savings. Using hybrid witnesses can save parties the substantial cost of retaining a professional expert.
  • Time savings. Unlike retained experts, who often require weeks or months to acquaint themselves with the facts and relationships of the parties in a case, hybrid witnesses may already have this knowledge due to their involvement in the underlying circumstances of the case.
  • Favorable jury perception. Juries typically perceive hybrid witnesses to be more credible than paid experts because hybrid witnesses generally form their observations and opinions without the persuasive influence of litigation or personal financial gain. A jury may view the fact that a hybrid witness is not receiving compensation for their testimony as indicative of a fair-minded witness as opposed to a biased or an easily influenced hired gun.


Unlike other experts, hybrid witnesses are limited to testifying based on their personal knowledge and observations they made in the ordinary course of their duties or through ground-level involvement in the events giving rise to the litigation (see, for example, Indianapolis Airport Auth. v. Travelers Prop. Cas. Co. of Am., 849 F.3d 355, 371 (7th Cir. 2017) (quoting Downey v. Bob's Discount Furniture Holdings, Inc., 633 F.3d 1, 6 (1st Cir. 2011))).

The distinction between a hybrid witness and other types of testifying experts is not always clear and, in some cases, an individual may be characterized as a hybrid witness regarding some opinions and a retained or specially employed expert regarding others (see, for example, Meredith v. Int'l Marine Underwriters, 2011 WL 1466436, at *4 (D. Md. Apr. 18, 2011)). This distinction is important because hybrid witnesses who testify based on their personal knowledge and observations are not subject to the detailed expert disclosure requirements set out in FRCP 26(a)(2)(B).

Before designating a hybrid witness, counsel should understand:

  • The types of cases in which hybrid witnesses are commonly used.
  • The limits of hybrid witness testimony.
  • How courts determine whether an individual is a hybrid witness.


Parties have used hybrid witnesses to support their claims in various types of cases, including, for example:

  • A personal injury case, where the treating physicians testified about the observations and conclusions they made during the course of treatment, including their opinions on what caused an injury or whether a treatment was necessary (see Lopez v. United States, 312 F. Supp. 3d 390, 397 n.9 (S.D.N.Y. 2018); Lebron v. Royal Caribbean Cruises, Ltd., 2018 WL 4539706, at *5 (S.D. Fla. Sept. 21, 2018); Farris v. Intel Corp., 493 F. Supp. 2d 1174, 1180 (D.N.M. 2007); but see Barnes v. Costco Wholesale Corp., 2019 WL 3101605, at *1 (D. Md. Apr. 18, 2019) (stating that having a treating physician testify about causation transforms the witness into a "classic expert" for which an FRCP 26(a)(2)(B) expert report is required)).
  • A case involving misappropriation of trade secrets, where a mechanical engineer employed by a party testified about the subject product's designs and features (see Feng Trading Co. Ltd. v. Quick Fitting, Inc., 2018 WL 6726557, at *3, *8 (D.R.I. Dec. 21, 2018)).
  • A product liability case, where engineers employed by a party testified about the subject product's development and design (see Companhia Energetica Portiguar v. Caterpillar Inc., 2017 WL 10775768, at *23-24 (S.D. Fla. June 12, 2017); United States v. Sierra Pac. Indus., 2011 WL 2119078, at *4-5 (E.D. Cal. May 26, 2011) (citing the 2010 Advisory Committee's Note to FRCP 26(a)(2)(C))).
  • A breach of contract case involving construction services, where construction workers testified about information they obtained and opinions they formed while performing construction tasks on the subject project (see Am. Prop. Constr. Co. v. Sprenger Lang Found., 274 F.R.D. 1, 4-5 (D.D.C. 2011)).
  • A case arising from a fire that occurred in connection with a renovation project, where an architect, accountants, and an engineer involved in the project testified based on their factual observations and the professional analyses they rendered during the project (see Beechgrove Redevelopment, L.L.C. v. Carter & Sons Plumbing, Heating & Air-Conditioning, Inc., 2009 WL 981724, at *6 (E.D. La. Apr. 9, 2009)).


Unless they provide an FRCP 26(a)(2)(B) expert report, hybrid witnesses cannot offer testimony that is based on:

  • Information that extends beyond the witness's personal involvement or eyewitness observations.
  • Information provided to the witness by an attorney.
  • Materials prepared in anticipation of litigation rather than in the ordinary course of the witness's work.
  • "After-the-fact" examinations or investigations, especially if they are performed in connection with litigation.

(See, for example, Goodman v. Staples the Office Superstore, LLC, 644 F.3d 817, 826 & n.2 (9th Cir. 2011) (holding that physician hybrid witnesses may testify about observations and opinions they formed during the course of a patient's treatment but not about any conclusions they made after reviewing a complete set of the patient's medical records); Avnet, Inc. v. Motio, Inc., 2016 WL 927194, at *4-5 (N.D. Ill. Mar. 4, 2016); Kondragunta v. Ace Doran Hauling & Rigging Co., 2013 WL 1189493, at *10-12 (N.D. Ga. Mar. 21, 2013); Ulbrick v UBR Prods., Inc., 2011 WL 500034, at *4 (E.D. Mich. Feb. 8, 2011) (holding that a mechanic hybrid witness may testify about his observations and opinions formed during his repair of the subject vehicle but not about opinions he formed during an after-the-fact examination conducted to determine the cause of the accident).)

Courts look to the source of the facts on which a witness's opinion is based when determining whether the witness is a hybrid witness or other type of testifying expert. Whether a witness was hired or paid to testify is not the sole deciding factor.


Courts look to the source of the facts on which a witness's opinion is based when determining whether the witness is a hybrid witness or other type of testifying expert. Whether a witness was hired or paid to testify is not the sole deciding factor (Avnet, Inc., 2016 WL 927194, at *5). The key inquiry is usually whether the witness's opinions are based on facts the witness learned or observations the witness made during the normal course of the witness's duties. If so, the court is likely to deem the witness a hybrid. By contrast, opinions the witness forms in anticipation of litigation or outside the normal course of the witness's duties are almost always considered expert opinions provided by a specially employed or retained expert (see above Limitations of Hybrid Witness Testimony).

As noted above, a court may deem an individual a hybrid witness regarding some opinions and a specially employed or retained expert regarding others (see above Scope of Hybrid Witness Testimony).

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Originally published 22 August, 2020

The content of this article is intended to provide a general guide to the subject matter. Specialist advice should be sought about your specific circumstances.