Mechanical Engineering Expert’s Testimony on the Mechanical Interlock Design Admitted

While preparing a roast in her Magic Chef 7-in-1 Multicooker, Tarsha Allgood was injured when the device’s lid opened causing its “scalding hot contents to be forcefully ejected from the pressure cooker.”

Allgood filed this lawsuit against CNA International, Inc. d/b/a MC Appliance Corporation raising claims under North Carolina law for inadequate warning, inadequate design, common law negligence, breach of express warranty, and breach of implied warranty.

CNA filed a motion to exclude the testimony of Allgood’s expert witness, David M. Rondinone, an engineer with Berkeley Engineering and Research, Inc.

Rondinone examined exemplars and other documents and materials, and concluded, among other things, that: (a) the mechanical interlock design intended to lock the lid is defective in that it fails to perform its function. This conclusion is based on, among other things, the geometric dimensions of the pin, lid, and cooker, which results in the interlock “providing very little resistance to the user;” and (b) “the presence of a defective pressure interlock increases the likelihood of the lid being opened and the cooker contents being expelled under pressure.” The touchstone of CNA’s argument is that Allgood threw away the device’s lid, so Rondinone could not test the actual multicooker Allgood used.

Mechanical Engineering Expert Witness

David Michael Rondinone has over 20 years of experience in mechanical engineering including design and failure analysis, fire suppression, explosions, flammability, flame arrestors, ignition, finite element analysis, accident reconstruction and crashworthiness, mechanical testing, failure of mechanical connections, dynamic stability of equipment and structures, pressure vessels and pipelines, medical implants and equipment, automotive component analysis and design.

Rondinone has a Masters and Ph.D in Mechanical Engineering from the University of California, Berkeley, where he previously received his B.S. in Engineering Physics and B.A. in Astrophysics.

Want to know more about the challenges David Rondinone has faced? Get the full details with our Challenge Study report.  

Discussion by the Court

The exemplar multicooker that Rondinone examined was used when it was purchased such that its prior history is unknown. CNA noted that the exemplar’s lid had a pre-existing scratch that Rondinone concluded means the lid was “force[d] open while under pressure by a prior user (an interlock override event).” CNA challenged the reliability of Rondinone’s opinion that the device was defectively designed because the mechanical interlock system could not meet the Underwriters Laboratories Cover Opening Standard.

According to CNA, Rondinone’s methodology relied on broad generalizations and failed to account for whether the exemplar met relevant Underwriters Laboratories’ standards before the exemplar was damaged. 

Allgood countered that Rondinone set forth his methodology in his report. He explained how he examined and measured the exemplar, including its interlock features, and considered relevant Underwriters Laboratories standards. He then concluded that the mechanical interlock design that is intended to lock the lid of the device is defective in that it fails to perform its intended function.

The Court agreed with Allgood that Rondinone’s conclusions are sufficiently reliable. Among other things, he explained how the exemplar he examined showed “linear defects in the coating which are consistent with wear from the lid locking pin sliding over the tab,” and that the pre-existing scratch on the lid he examined could be the result of the lid being opened under pressure despite the sliding pin lock being held in place by the float valve.

CNA’s remaining arguments failed to persuade the Court. That Rondinone did not take measurements that CNA deems critical, failed to perform a statistical or comparative analysis, or reached his conclusions based on a “single nonrepresentative data point,” are fair points for cross-examination.

Held

The Court denied the Defendant’s motion to exclude the testimony of David Rondinone.

Key Takeaway:

The Court held that Rondinone’s opinions are appropriately based on sufficient data, an examination of an exemplar, and a reliable application to the facts of this case. His testimony would also assist the fact finder with determining whether a defect existed at the relevant time, and the methodology underlying his conclusions is sound and sufficiently reliable for trial.

To the extent CNA wishes to challenge the facts forming the basis of Rondinone’s opinions, including the impact, if any, that examining an exemplar had on his conclusions, it may do so on cross-examination. Although the facts on which an expert bases his opinion must have some basis in the record, there is no requirement that the basis must consist of undisputed evidence.

Case Details:

Case Caption:	Allgood V. CNA International, Inc.
Docket Number:	1:23cv462
Court Name:	United States District Court, Illinois Northern
Order Date:	September 3, 2025