The panel majority held, in an originally unpublished disposition, that the district court did so by misapplying Rule 702. See Tekoh v. County of Los Angeles, 75 F.4th 1264 (9th Cir. 2023) ("Tekoh II"). That decision was correct, and I join our court's decision to not rehear the case en banc.

At the merits stage, we review a district court's ruling on the admissibility of expert testimony under an abuse of discretion standard. Tekoh v. County of Los Angeles, 75 F.4th 1264, 1265 (9th Cir. 2023) (citing United States v. Redlightning, 624 F.3d 1090, 1110 (9th Cir. 2010)). We review "a summary judgment ruling de novo." Zellmer v. Meta Platforms, Inc., 104 F.4th 1117, 1121 (9th Cir. 2024) (citation omitted).

We have held that "false confessions are an issue beyond the common knowledge of the average layperson," and juries benefit from "expert knowledge about the science of coercive interrogation tactics." Tekoh v. County of Los Angeles, 75 F.4th 1264, 1266 (9th Cir. 2023).

A district court's evidentiary rulings are reviewed for abuse of discretion. See Tekoh v. County of Los Angeles, 75 F.4th 1264, 1265 (9th Cir. 2023). A district court's order granting summary judgment is reviewed de novo.

Nichols offered expert testimony to rebut Pinedo's assertion of an inadequate investigation, cf. United States v. Rivera, 43 F.3d 1291, 1295 (9th Cir. 1995), and did not improperly comment on the specific facts of this case or on Radlinski's performance as an investigator. See Tekoh v. County of Los Angeles, 75 F.4th 1264, 1266 (9th Cir. 2023). Finally, any error would have been harmless.

(cleaned up)). Rule 702 also requires opinion evidence to be “helpful” to the trier of fact, which is another way of describing a “relevance inquiry.” Tekoh v. County of Los Angeles, 75 F.4th 1264, 1265 (9th Cir. 2023). “Expert testimony which does not relate to any issue in the case is not relevant and, ergo, non-helpful.”