Also known as: analytical gaps
Written by attorneys · grounded in primary & secondary sources — see below
A disconnect between an expert witness's supporting data or methodology and the conclusion offered in testimony. The gap renders the opinion unreliable when the expert's reasoning lacks a sufficient factual or methodological foundation.
Abigail Alvarez and other investors sued Apex Dynamics for securities fraud after the company allegedly misrepresented its fund's risk level. Their economist expert calculated damages by comparing fund returns to a market index he selected without citing any empirical studies or industry practice to justify the choice. The district court excluded the testimony after finding the unexplained benchmark left the damages figure untethered from the underlying data.
Adrian Aguilar lost his hand when a press guard failed at Alpine Mining's plant. He offered a mechanical engineer who inspected the machine for one hour and concluded the guard was defective based on its placement and thin material. The engineer took no measurements, ran no simulations, and cited no specific standards. The district court excluded the testimony because the visual observations alone did not support the design-defect conclusion.
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Appellate courts review the exclusion for abuse of discretion. The trial judge acts as gatekeeper and may exclude an opinion when the leap from data to conclusion lacks adequate support in facts or methodology.
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An analytical gap can render the testimony inadmissible. When the expert's reasoning is not reliably connected to the data, the court may exclude the opinion rather than admit it and leave the flaw for cross-examination.
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Experience alone does not close the gap. The expert must still demonstrate a reliable connection between the data considered and the specific conclusion offered. Otherwise the court may find the opinion unreliable.
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…is connected to existing data only by the ipse dixit of the expert. A court may conclude that there is simply too great an analytical gap between the data and the opinion proffered. See Turpin v. Merrell Dow Pharmaceuticals, Inc. , 959 F. 2d 1349, 1360 (CA6), cert. denied, 506 U. S. 826 (1992). That is what the District…