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Expert Witness Insights by Area of Expertise
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Areas of Expertise :
Patent, Intellectual Property, Civil Litigation, Evidence Analysis & Preservation, Engineering
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In federal patent litigation, an important technical witness may be someone inside the company. It may be an engineer, inventor, product manager, or other technical employee who has firsthand knowledge of the product, patent, or development history.
That can be helpful, but it can also create privilege and work-product problems if that same person has already worked closely with counsel behind the scenes. A technical employee may help counsel understand the product, the patent, prior technical materials, or the technical issues that could shape the case. If that person is later disclosed as a non-reporting testifying expert, materials counsel expected to keep protected may become discovery targets.
This guide explains how Rule 26 treats reporting experts, non-reporting experts, and non-testifying trial-preparation experts, why the district court Luminara discovery rulings matter, and what attorneys should consider before designating an internal technical witness in a federal patent case.
The expert’s classification matters. Reporting experts, non-reporting testifying experts, and non-testifying trial-preparation experts do not carry the same disclosure duties or communication protections.
Rule 26(a)(2)(B) applies to witnesses retained or specially employed to provide expert testimony, as well as employees whose duties regularly involve giving expert testimony. These experts must provide a written report that includes their opinions, the basis and reasons for those opinions, the facts or data considered, and other required information.
Rule 26(a)(2)(C) applies when a witness is not required to provide a written report, unless otherwise stipulated or ordered by the court. The disclosure must state the subject matter of the testimony and summarize the facts and opinions the witness is expected to offer.
That lighter disclosure burden can be useful, but it comes with a catch. Rule 26(b)(4)(C) protects many attorney communications with Rule 26(a)(2)(B) reporting experts, subject to limited exceptions. But the Advisory Committee Notes make clear that Rule 26(b)(4)(C) does not itself protect communications with Rule 26(a)(2)(C) experts.
Some communications may still be protected by attorney-client privilege or work-product doctrine, but attorneys should not assume Rule 26(b)(4)(C) supplies that protection. A non-reporting designation may reduce the written-report burden while increasing discovery risk if the witness has already reviewed sensitive litigation materials.
Non-reporting expert witnesses in federal patent litigation can create attorney-client privilege and work-product risks when internal engineers, inventors, or other technical employees move from behind-the-scenes consulting roles into testifying roles. This article explains Rule 26 protections and disclosure requirements, the discovery implications of the Luminara rulings, Rule 702 reliability considerations, and practical steps attorneys can take to manage sensitive communications, technical materials, and expert designations.
Patent Dispute
Patent Infringement
Patent Claim Mapping
Prior Art
Litigation
Litigation Support
Evidence Analysis
Document Security
In federal patent litigation, an important technical witness may be someone inside the company. It may be an engineer, inventor, product manager, or other technical employee who has firsthand knowledge of the product, patent, or development history.
That can be helpful, but it can also create privilege and work-product problems if that same person has already worked closely with counsel behind the scenes. A technical employee may help counsel understand the product, the patent, prior technical materials, or the technical issues that could shape the case. If that person is later disclosed as a non-reporting testifying expert, materials counsel expected to keep protected may become discovery targets.
This guide explains how Rule 26 treats reporting experts, non-reporting experts, and non-testifying trial-preparation experts, why the district court Luminara discovery rulings matter, and what attorneys should consider before designating an internal technical witness in a federal patent case.
The expert’s classification matters. Reporting experts, non-reporting testifying experts, and non-testifying trial-preparation experts do not carry the same disclosure duties or communication protections.
Rule 26(a)(2)(B) applies to witnesses retained or specially employed to provide expert testimony, as well as employees whose duties regularly involve giving expert testimony. These experts must provide a written report that includes their opinions, the basis and reasons for those opinions, the facts or data considered, and other required information.
Rule 26(a)(2)(C) applies when a witness is not required to provide a written report, unless otherwise stipulated or ordered by the court. The disclosure must state the subject matter of the testimony and summarize the facts and opinions the witness is expected to offer.
That lighter disclosure burden can be useful, but it comes with a catch. Rule 26(b)(4)(C) protects many attorney communications with Rule 26(a)(2)(B) reporting experts, subject to limited exceptions. But the Advisory Committee Notes make clear that Rule 26(b)(4)(C) does not itself protect communications with Rule 26(a)(2)(C) experts.
Some communications may still be protected by attorney-client privilege or work-product doctrine, but attorneys should not assume Rule 26(b)(4)(C) supplies that protection. A non-reporting designation may reduce the written-report burden while increasing discovery risk if the witness has already reviewed sensitive litigation materials.
Luminara arose from patent litigation involving flameless candle technology. The Federal Circuit’s 2016 opinion provides the patent-case background, but the privilege issue discussed here comes from a separate discovery ruling in the same underlying litigation, often referred to as Luminara III.
In Luminara III, the court applied a broad reading of what a Rule 26(a)(2)(C) expert “considered.” Under that approach, materials considered by a non-reporting expert may include documents and communications the expert generated, saw, read, reviewed, or reflected on, whether or not the expert ultimately relied on them when forming the opinion.
That reasoning did not stay confined to patent litigation. In City of Wyoming, a separate products liability case involving flushable wipes, the court discussed the Luminara discovery decisions and applied the same broad approach when deciding what a non-reporting employee expert had to produce. For patent litigators, the point is practical: courts may take a broad view of what a non-reporting expert considered, especially when an internal technical employee has moved between behind-the-scenes consulting and expert testimony.
That does not mean privilege disappears the moment a technical employee becomes an expert witness. It is more of a warning sign than a fixed rule every court will apply the same way. The practical concern is that once a technical witness offers opinions, opposing counsel may ask what the witness considered while forming those opinions, even if the witness did not ultimately rely on every document reviewed.
For patent teams, the same concern may reach technical records, testing materials, internal communications, early technical analyses, and other documents the witness reviewed while forming opinions.
For example, in a patent case, an inventor may help counsel understand an accused product and comment on an early technical analysis before anyone decides whether that person will testify. If that inventor is later disclosed as a non-reporting expert, opposing counsel may ask what the inventor saw, reviewed, or reflected on before forming the opinion.
What looked efficient early in the case can become difficult to defend during discovery.
These problems can happen when a witness’s role changes over time. A technical employee may start as a behind-the-scenes resource, then later be considered for expert testimony because of firsthand knowledge of the product, patent, source materials, or development history.
Risky patterns include:
These issues can lead to motions to compel, privilege disputes, deposition problems, and Rule 37(c)(1) exclusion arguments if a party fails to provide required Rule 26 information or identify a witness.
A careful privilege plan does not save unreliable expert testimony. Even if counsel handles attorney communications and work-product issues well, the testimony still has to stand on its own.
Under Rule 702, a witness must be qualified by knowledge, skill, experience, training, or education. The proponent must also show that it is more likely than not that the expert’s testimony will help the trier of fact, is based on sufficient facts or data, is the product of reliable principles and methods, and reflects a reliable application of those principles and methods to the facts of the case.
For technical experts in patent cases, reliability can turn on whether the witness can explain:
A strong technical witness should be able to explain how they reached the opinion, not just state the conclusion. Courts are looking for a reliable path from the evidence to the opinion.
Privilege problems are much easier to prevent than fix. The safest approach is to decide the witness’s role before sensitive materials are shared.
Before disclosing a non-reporting testifying expert, counsel should:
If an internal technical employee has already helped counsel behind the scenes, counsel should carefully evaluate the discovery consequences before later disclosing that person as a testifying expert.
The goal is not to make expert preparation more complicated. It is to avoid losing control over materials counsel expected to keep protected while making sure the testimony can withstand discovery and admissibility challenges.
Can attorney-client privilege protect communications with a non-reporting testifying expert?
Sometimes. It depends on the communication, the witness’s role, and the court. The main concern is that Rule 26(b)(4)(C) does not itself protect attorney communications with Rule 26(a)(2)(C) experts.
Why are patent cases especially sensitive?
Patent cases may involve employees who understand product design, prior art, testing, claim analysis, or technical development history. Those same employees may also have received attorney-guided analysis.
What is the safest way to protect early technical analysis?
Where practical, use a separate non-testifying trial-preparation expert when testimony is not expected, control document access, and decide early whether any internal technical witness may later testify.
Can a poor non-reporting expert disclosure lead to exclusion?
Yes. If a party fails to provide required Rule 26 information or identify a witness, Rule 37(c)(1) can bar use of that information or witness unless the failure was substantially justified or harmless.
Luminara arose from patent litigation involving flameless candle technology. The Federal Circuit’s 2016 opinion provides the patent-case background, but the privilege issue discussed here comes from a separate discovery ruling in the same underlying litigation, often referred to as Luminara III.
In Luminara III, the court applied a broad reading of what a Rule 26(a)(2)(C) expert “considered.” Under that approach, materials considered by a non-reporting expert may include documents and communications the expert generated, saw, read, reviewed, or reflected on, whether or not the expert ultimately relied on them when forming the opinion.
That reasoning did not stay confined to patent litigation. In City of Wyoming, a separate products liability case involving flushable wipes, the court discussed the Luminara discovery decisions and applied the same broad approach when deciding what a non-reporting employee expert had to produce. For patent litigators, the point is practical: courts may take a broad view of what a non-reporting expert considered, especially when an internal technical employee has moved between behind-the-scenes consulting and expert testimony.
That does not mean privilege disappears the moment a technical employee becomes an expert witness. It is more of a warning sign than a fixed rule every court will apply the same way. The practical concern is that once a technical witness offers opinions, opposing counsel may ask what the witness considered while forming those opinions, even if the witness did not ultimately rely on every document reviewed.
For patent teams, the same concern may reach technical records, testing materials, internal communications, early technical analyses, and other documents the witness reviewed while forming opinions.
For example, in a patent case, an inventor may help counsel understand an accused product and comment on an early technical analysis before anyone decides whether that person will testify. If that inventor is later disclosed as a non-reporting expert, opposing counsel may ask what the inventor saw, reviewed, or reflected on before forming the opinion.
What looked efficient early in the case can become difficult to defend during discovery.
These problems can happen when a witness’s role changes over time. A technical employee may start as a behind-the-scenes resource, then later be considered for expert testimony because of firsthand knowledge of the product, patent, source materials, or development history.
Risky patterns include:
These issues can lead to motions to compel, privilege disputes, deposition problems, and Rule 37(c)(1) exclusion arguments if a party fails to provide required Rule 26 information or identify a witness.
A careful privilege plan does not save unreliable expert testimony. Even if counsel handles attorney communications and work-product issues well, the testimony still has to stand on its own.
Under Rule 702, a witness must be qualified by knowledge, skill, experience, training, or education. The proponent must also show that it is more likely than not that the expert’s testimony will help the trier of fact, is based on sufficient facts or data, is the product of reliable principles and methods, and reflects a reliable application of those principles and methods to the facts of the case.
For technical experts in patent cases, reliability can turn on whether the witness can explain:
A strong technical witness should be able to explain how they reached the opinion, not just state the conclusion. Courts are looking for a reliable path from the evidence to the opinion.
Privilege problems are much easier to prevent than fix. The safest approach is to decide the witness’s role before sensitive materials are shared.
Before disclosing a non-reporting testifying expert, counsel should:
If an internal technical employee has already helped counsel behind the scenes, counsel should carefully evaluate the discovery consequences before later disclosing that person as a testifying expert.
The goal is not to make expert preparation more complicated. It is to avoid losing control over materials counsel expected to keep protected while making sure the testimony can withstand discovery and admissibility challenges.
Can attorney-client privilege protect communications with a non-reporting testifying expert?
Sometimes. It depends on the communication, the witness’s role, and the court. The main concern is that Rule 26(b)(4)(C) does not itself protect attorney communications with Rule 26(a)(2)(C) experts.
Why are patent cases especially sensitive?
Patent cases may involve employees who understand product design, prior art, testing, claim analysis, or technical development history. Those same employees may also have received attorney-guided analysis.
What is the safest way to protect early technical analysis?
Where practical, use a separate non-testifying trial-preparation expert when testimony is not expected, control document access, and decide early whether any internal technical witness may later testify.
Can a poor non-reporting expert disclosure lead to exclusion?
Yes. If a party fails to provide required Rule 26 information or identify a witness, Rule 37(c)(1) can bar use of that information or witness unless the failure was substantially justified or harmless.
Patent Dispute
Patent Infringement
Patent Claim Mapping
Prior Art
Litigation
Litigation Support
Evidence Analysis
Document Security
Expert Witness Insights by Area of Expertise
Expert Witness Insights by Area of Expertise