Medical device engineer
Expert class library · Mass tort and product liability · Either side
A biomedical, mechanical or materials engineer who analyzes the design, testing and failure modes of implants and devices such as knee replacements, IVC filters and surgical lasers. Courts admit engineering opinions on failure mechanisms and testing when grounded in analysis or calculation, even without experience on the specific device, but exclude defect opinions built on litigation driven case reports without failure rate data and opinions on manufacturing controls outside the engineer's expertise.
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Questions this testimony turns on
- What data show that this device fails more often than comparable devices, rather than at the background rate for the device type?
- Did the engineer test, model or calculate the failure mechanism, or rely on case reports and complaints?
- Is the engineer qualified in the specific subject, such as stress analysis, manufacturing controls or thermal effects, on which each opinion is offered?
- How does the opinion connect the alleged design flaw to the failure that occurred in this patient?
- Were the opinions developed independently of the litigation and exposed to peer review?
Methods
- Design history file review
- Bench and fatigue testing
- Failure mode and effects analysis
- Retrieved device analysis
- Finite element and stress analysis
- Engineering calculations of energy and heat transfer
How the testimony is attacked
- No failure rate data. Defendants show that the engineer cannot establish that the device fails more often than alternatives. In Sprafka v. Medical Device Business Services the Eighth Circuit affirmed exclusion of a biomedical engineer whose knee implant defect opinion rested on two case studies and anecdotes while registry data suggested similar revision rates.
- Litigation driven opinions. Challengers stress that opinions prepared only for litigation, without peer review, need other indicia of reliability. Sprafka applied the 2023 amendment to Rule 702 and treated the litigation origin of the opinions as weighing against admission.
- Outside the engineer's field. Opponents split an engineer's report by subject. In Tillman v. C.R. Bard the court admitted mechanical engineers' fracture and testing opinions on an IVC filter but excluded their opinions on manufacturing process variability because their expertise was stress and strain analysis.
- No experience with the specific device. Proponents answer that engineers need not have worked on the device itself. In Cohen v. Boston Scientific the District of New Hampshire held a mechanical engineer with materials and biomedical training qualified to analyze a surgical laser despite no prior laser experience.
- No physical testing. Defendants argue that calculations without testing are unreliable. Cohen held that testing is a useful guidepost but not a requirement, and admitted the engineer's heat transfer calculations, reserving one issue for an evidentiary hearing.
What the public record shows
Courts have filed at least 23 opinions since 2015 that discuss this class of testimony and cite Daubert or Rule 702, as of October 3, 2026. Three that show how courts handle this class of testimony:
| Outcome | Case | Court | Year | Why |
|---|---|---|---|---|
| Excluded | Sprafka v. Medical Device Business Services, Inc.139 F.4th 656 | 8th Cir. | 2025 | The Eighth Circuit affirmed exclusion under amended Rule 702 of a biomedical engineer's opinion that a knee replacement system was defectively designed, because it rested on two case studies and anecdotes without reliable data on its debonding rate compared with other systems. |
| Limited | Tillman v. C.R. Bard, Inc.96 F. Supp. 3d 1307 | M.D. Fla. | 2015 | The court admitted two mechanical engineers' opinions on IVC filter fracture and the adequacy of the manufacturer's testing for tilt, perforation and migration, but excluded their opinions on manufacturing process variability as outside their stress analysis expertise. |
| Admitted | Cohen v. Boston Scientific Corp.2024 DNH 026 | D.N.H. | 2024 | The court denied, without prejudice, motions to exclude a mechanical engineer's opinions that a surgical laser system heated irrigation saline enough to burn the patient's bladder, holding him qualified without device specific experience and finding that calculations need not be confirmed by testing. |
Each case links to the free opinion text on CourtListener.
In federal court: amended Rule 702
In federal court, 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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Updated October 3, 2026. How this page is built: rulings are found by searching court opinions on CourtListener. The summaries are written by AI working from the full text of each opinion, and every citation and link is checked automatically. 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. Spotted an error? Tell us.