Patent invalidity and prior-art expert
Expert class library · Intellectual property · Defense side
Opines that asserted claims are anticipated or obvious in light of the prior art as understood by a person of ordinary skill. Also addresses written description and enablement.
What this expert is retained to answer
- What is the level of ordinary skill in the art, and does the expert possess at least that skill?
- Which prior art references would a skilled artisan have combined, and why would that person have been motivated to combine them?
- Does the expert assess the claimed invention as a whole, or use the claims as a roadmap to pick elements out of the prior art?
- Is each reference the expert relies on disclosed in the invalidity contentions and actually prior art?
- Do secondary considerations such as commercial success undercut the obviousness opinion?
Methods
- Anticipation analysis
- Obviousness and motivation to combine
- Secondary considerations rebuttal
- Person of ordinary skill definition
How the testimony is attacked
- Witness lacks skill in the pertinent art. Patentees argue that a patent lawyer or other witness without technical expertise cannot testify on obviousness. In Sundance v. DeMonte Fabricating the Federal Circuit held it was an abuse of discretion to admit a patent law expert's opinion that a skilled artisan would combine the references, because he was not qualified in the relevant art.
- Report written by counsel. Patentees show that the expert's report copies the invalidity contentions nearly word for word. In Numatics v. Balluff the court struck the challenged sections of the defense expert's report because counsel drafted them and the expert spent only a couple of hours reviewing a report that reproduced the contentions down to the punctuation.
- No basis for the motivation to combine. Patentees argue that the expert assumes the references would be combined without explaining why. The Numatics court found the report gave no basis for combining the prior art and that the expert did not understand the factors relevant to obviousness.
- Hindsight use of the claims as a roadmap. Patentees cite deposition admissions that the expert used the claims to find elements in the prior art. In Icon-IP v. Specialized Bicycle Components the court declined to exclude on that basis because the report disclosed which references would be combined and how and why.
- Unexplained definition of ordinary skill. Patentees attack a person of ordinary skill definition stated without discussing the factors behind it. The Icon-IP court held that identifying the level of skill was proper and that no rule requires a report to walk through each factor.
- References missing from the invalidity contentions. Patentees move to strike opinions resting on prior art never disclosed in the contentions. The Icon-IP court struck the expert's opinions on one undisclosed reference under the patent local rules while admitting his other obviousness opinions.
What the public record shows
A deliberately narrow CourtListener search, obviousness AND "motivation to combine" AND "invalidity expert" AND (Daubert OR "Rule 702"), returned 1 opinions filed since 2015, as of October 2, 2026; broader searches return more. Three that show how courts handle this class of testimony:
| Outcome | Case | Court | Why |
|---|---|---|---|
| Excluded | Sundance, Inc. v. DeMonte Fabricating Ltd.550 F.3d 1356 | Fed. Cir. 2008 | The Federal Circuit held the district court abused its discretion under Rule 702 by letting the defendant's patent law expert, who lacked technical expertise in the art, testify on invalidity and on a skilled artisan's motivation to combine references. |
| Excluded | Numatics, Inc. v. Balluff, Inc.66 F. Supp. 3d 934 | E.D. Mich. 2014 | The court struck the challenged sections of the defendant's invalidity expert's report because counsel wrote them by copying the invalidity contentions, and the expert gave no basis for combining the prior art and did not understand the governing obviousness factors. |
| Admitted | Icon-IP Pty Ltd. v. Specialized Bicycle Components, Inc.87 F. Supp. 3d 928 | N.D. Cal. 2015 | The court rejected the patentee's argument that the defendant's engineer offered conclusory obviousness opinions, finding that he adequately explained which references would be combined and how and why, and that his roadmap admission did not require exclusion. |
Each case links to the free opinion text on CourtListener.
Under amended Rule 702
Since December 1, 2023, Rule 702 says expressly that the party offering an expert must show the court it is more likely than not that the testimony meets each requirement: that it rests on sufficient facts or data, uses reliable methods, and reflects a reliable application of those methods to the case. Questions about the basis of an opinion are no longer automatically matters of weight for the jury. For how the circuits have applied the amendment, see the Rule 702 tracker, which follows each court of appeals; for what that means for preparing or attacking this class of expert, see the guide on amended Rule 702.
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Last reviewed October 2, 2026. How this page is built: rulings are found by searching court opinions on CourtListener, and each one is read in the opinion before it is summarised here; outcomes are labelled by what the court did with the expert's testimony. No individual expert is named. This page summarises public decisions for orientation and is not legal advice; read the opinion before relying on any ruling.