Daubert Standard

Daubert v. Merrell Dow Pharmaceuticals, Inc. (S.Ct. 1993) established the framework for admissibility of expert testimony in federal court under Federal Rule of Evidence 702: RULE 702 (as amended to codify Daubert): expert testimony is admissible only if: (a) the expert's scientific, technical, or other specialized knowledge will help the trier of fact understand the evidence; (b) the testimony is based on sufficient facts or data; (c) the testimony is the product of reliable principles and methods; (d) the expert has reliably applied the principles and methods to the facts of the case; GATEKEEPING ROLE: the district court acts as a gatekeeper — it must screen expert testimony before trial (typically via Daubert motions in limine) to ensure it meets the reliability threshold; the jury does NOT hear unreliable expert testimony; PATENT CASE CONTEXT: patent litigation relies heavily on expert testimony for: (1) TECHNICAL ISSUES: claim construction (Markman), infringement, invalidity, claim scope, priority, and written description; (2) DAMAGES ISSUES: reasonable royalty rate (Georgia-Pacific factors), lost profits, market size, price erosion, comparable licenses; BOTH TYPES of experts face Daubert scrutiny; a defective damages expert can devastate a patent case that was otherwise winnable on the merits; KUMHO TIRE v. CARMICHAEL (S.Ct. 1999): extended Daubert to all expert testimony — not just 'scientific' testimony; technical and professional experts in patent cases are fully subject to Daubert.

The original Daubert opinion provided four non-exclusive factors for evaluating reliability of scientific testimony — courts use these as a flexible guide, not a rigid checklist: (1) TESTABILITY: can the expert's theory or methodology be tested? Has it been tested? A theory that is inherently untestable (cannot be falsified) is a red flag; in patent cases, a damages expert who creates a custom royalty model that has never been empirically validated is vulnerable; (2) PEER REVIEW AND PUBLICATION: has the expert's methodology been published in peer-reviewed literature? Publication exposes the methodology to scrutiny by the scientific community; however, patent damages methodologies rarely appear in peer-reviewed journals — courts adapt this factor; (3) KNOWN OR POTENTIAL ERROR RATE: what is the error rate for the expert's methodology? What are the standards controlling the technique's operation? A technique with high error rates is less reliable; (4) GENERAL ACCEPTANCE: is the methodology generally accepted in the relevant scientific or professional community? Frye's 'general acceptance' test lives on as ONE factor within Daubert's broader inquiry; ADDITIONAL FACTORS: courts also consider (5) whether the testimony was developed for litigation vs. based on pre-existing research; (6) whether the expert is testifying about matters growing naturally from research they conduct as part of their regular professional work; (7) whether the expert adequately accounts for alternative explanations; APPLICATION IN PATENT CASES: for technical experts (infringement/invalidity), courts focus on whether the expert has used reliable methodology to compare the claim to the accused product or prior art; for damages experts, courts focus on whether the royalty rate methodology, license comparisons, or lost profits analysis are grounded in accepted economic principles.

Patent damages expert testimony is among the most frequently challenged under Daubert, particularly reasonable royalty opinions: REASONABLE ROYALTY — COMMON GROUNDS FOR EXCLUSION: (1) GEORGIA-PACIFIC MISAPPLICATION: expert lists all 15 Georgia-Pacific factors but applies them without factual basis or explanation; courts require that each factor be tied to specific facts of the case; a formulaic recitation of factors without substantive analysis is excludable as unreliable; (2) ENTIRE MARKET VALUE RULE ABUSE: expert uses the entire product price as royalty base without demonstrating that the patented feature drives customer demand for the whole product (LaserDynamics rule); (3) COMPARABLE LICENSE COMPARISONS: expert relies on licenses that are not technologically or economically comparable to the hypothetical negotiation; must explain basis for any adjustments; (4) ROYALTY STACKING PROBLEMS: expert ignores royalty stacking in a field with multiple essential patents; (5) GAMING THE HYPOTHETICAL NEGOTIATION DATE: expert sets negotiation date to maximize damages without factual basis; LOST PROFITS — COMMON GROUNDS FOR EXCLUSION: (1) PANDUIT FACTOR 2 FAILURE: assumes no acceptable non-infringing substitutes exist without adequate market analysis; (2) CAUSATION FLAWS: fails to tie lost sales to specific infringing features or proves causation with insufficient analysis; (3) CALCULATION ERRORS: arithmetic errors, incorrect margin calculations, double-counting of damages; RESOLVABLE vs. EXCLUDABLE ISSUES: courts differ on whether methodological flaws go to weight (jury decides) vs. admissibility (court excludes); courts increasingly exclude outright rather than leaving weak methodologies to cross-examination.

Technical experts in patent cases face Daubert challenges on both infringement and invalidity opinions: INFRINGEMENT EXPERT CHALLENGES: (1) CLAIM CONSTRUCTION IMPROPRIETY: expert applies a claim construction that the court has not adopted or that is legally incorrect; expert testimony on claim construction is often excluded because claim construction is a pure question of law for the court; (2) COMPARISON METHODOLOGY: expert compares the accused product to the embodiment disclosed in the patent, not to the claim language itself (the legally correct comparison is claim vs. product); (3) FUNCTION-WAY-RESULT TEST FOR DOE: expert asserts doctrine of equivalents infringement without rigorously applying the function-way-result test to each element; conclusory DOE opinions are frequently excluded; (4) MISSING ELEMENT: expert's infringement analysis fails to account for all claim elements — if any element is missing from the accused product, there is no infringement; (5) REVERSE ENGINEERING: if the expert relied on reverse engineering, the methodology must be reliable and reproducible; INVALIDITY EXPERT CHALLENGES: (1) CLAIM ELEMENT MAPPING: expert maps prior art to claimed elements without adequate support; conclusory statements that 'reference X teaches element Y' without explanation are excludable; (2) LEVEL OF ORDINARY SKILL: expert fails to define the person of ordinary skill in the art with reasonable precision; (3) HINDSIGHT RECONSTRUCTION: expert uses knowledge of the invention to reconstruct why prior art references would have been combined — courts watch for hindsight bias; (4) WRITTEN DESCRIPTION / ENABLEMENT: expert opinion must be based on what the specification actually discloses, not on what the applicant now claims to have meant.

Procedural mechanics of Daubert motions in federal patent cases: TIMING: (1) MOTIONS IN LIMINE: Daubert challenges are typically filed as motions in limine before trial, after expert reports are exchanged during discovery; the briefing schedule follows the court's scheduling order — usually 30–60 days after expert depositions; (2) DAUBERT HEARINGS: courts may (but are not required to) hold evidentiary hearings ('Daubert hearings') where the challenged expert testifies about their methodology; alternatively, courts decide on briefs and expert reports alone; (3) SUMMARY JUDGMENT INTERACTION: if the plaintiff's damages expert is excluded, the plaintiff may have no evidence of damages and face summary judgment on the damages issue (though a new expert may sometimes be substituted); STANDARD: the district court has broad discretion; the Federal Circuit reviews Daubert rulings for abuse of discretion — deferential standard; the Federal Circuit does NOT de novo review which methodology is 'better'; PARTIAL EXCLUSION: courts frequently exclude parts of an expert's opinion while allowing other parts; an expert may be qualified but offer an opinion on one topic (e.g., willfulness) that is outside their expertise; RECOVERY AFTER EXCLUSION: once an expert is excluded, the party generally cannot simply substitute a new expert — the case proceeds without that testimony; in egregious cases, total exclusion of a damages expert can result in nominal damages or zero damages; APPORTIONMENT EXPERT: Daubert frequently targets whether damages experts properly apportioned the royalty base and rate to the patented feature — a critical issue in the era of multi-component products.