From Credibility to Admissibility: Reblending the Expert Playbook Under Rule 702

The recent decision in Mendoza v. SharkNinja Operating, LLC by the District of Colorado offers a practical illustration of how federal courts are applying the heightened reliability standard under the 2023 amendments to Rule 702.^[1]In Mendoza, the plaintiff alleged that the defendant’s NutriNinja blender was defectively designed, causing the blender’s contents to heat up and pressurize, resulting in an explosive ejection of hot liquid during normal use. To support these claims, the plaintiff offered an expert who provided opinions on the blender’s design and related safety issues.^[2]The court excluded all of the plaintiff’s expert’s opinions, finding that none met the reliability threshold required by Rule 702.

First, the plaintiff’s expert concluded that the design of the NutriNinja blender could have caused the liquid to explode during or after blending.^[3]However, to support this opinion, the plaintiff’s expert conducted only limited testing with cold water at different blending intensities for one minute. Despite these limitations, the expert nevertheless concluded that the alleged incident likely involved warm or hot water and greater than one minute of blending—neither of which he tested.^[4]

The court acknowledged that “testing is not always required to satisfy the reliability threshold of Rule 702,” but emphasized that it is  “particularly important when a proposed expert relies on novel theories or where the basis of the expert’s opinions is subject to debate.”^[5]Here, the lack of testing under analogous circumstances and the absence of scientific principles or methodology seriously undermined the reliability of the expert’s opinions.^[6]Indeed, the court found “nothing” in the expert’s report to support the conclusion that using cold or warm liquids for any period could cause an explosive release, nor any scientific methodology by which the expert reached his conclusion.^[7]

The plaintiff contended that the defendant’s Rule 702 challenges were “of weight, not admissibility.”^[8]The court disagreed, citing the 2023 amendments to Rule 702, which clarify that “the proponent of the testimony must show that it is ‘more likely than not’ that the expert’s testimony is based on sufficient facts or data and is the product of reliable principles and methods.”^[9]The court found that the design-defect opinions offered by the plaintiff’s expert did not satisfy this standard, as a court is “not required to admit opinion evidence that is connected to existing data only by the ipse dixit of the expert.”^[10]

Second, the plaintiff’s expert proposed several alternative designs—a pressure relief valve, a cup with a leak path, and alternative materials—to mitigate the alleged dangers of the defendant’s NutriNinja blender.^[11]The court rejected each as unreliable under Rule 702. The court noted that the expert failed to explain how these alternative designs were feasible, did not address comparability to other products, did not conduct any testing, and did not consider the operating conditions and safety tradeoffs of each.^[12]For example, he suggested a different material to mitigate the alleged blender issues, but did not specify any current materials, relevant mechanical or thermal properties, or their performance under similar temperatures, which were all left only to conjecture.^[13]

Third and lastly, the court excluded the remaining opinions of the plaintiff’s expert regarding the adequacy of warnings contained on the NutriNinja blender and the adequacy of the defendant’s “risk assessment.”  The court observed that he did not have “any relevant experience or education related to product warnings” and provided no “supporting explanation” for his risk assessment opinion.^[14]

Because “expert testimony is required” to prove the plaintiff’s design-defect claim and the court had excluded the plaintiff’s sole expert, leaving the plaintiff “without any admissible expert testimony on that topic,” summary judgment was therefore appropriate.^[15]The court, accordingly, granted the defendant’s motion.

Key Takeaways

 Like other recent Rule 702 decisions, Mendoza highlights that, under the amended Rule 702, corporate defendants can successfully defeat product-defect claims by exposing gaps in the opposing expert’s methodology, such as failure to test under relevant conditions, lack of comparative analysis, or unsupported alternative designs. The decision shows that courts are willing to exclude expert opinions that do not meet the reliability standard, paving the way for summary judgment even in cases involving complex allegations.

---

[1] Mendoza v. SharkNinja Operating, LLC, 2025 WL 2696876 (D. Colo. Sep. 22, 2025).

[2] Id. at *2.

[3] Id. at *3.

[4] Id.

[5] Id. at *4 (citations omitted).

[6] Id.

[7] Id.

[8] Id.

[9] Id.

[10] Id. at *5 (citation omitted).

[11] Id.

[12] Id. at *5–7.

[13] Id. at *7.

[14] Id. at *8.

[15] Id. at *11.