In Estate of Barabin v. AstenJohnson, Inc., 740 F.3d 457 (9th Cir. 2014) (Nos. 10-36142, 11-35020) (en banc), the Ninth Circuit reviewed en banc a district court’s decision to admit expert testimony from two asbestos experts tendered by plaintiff, who espoused the controversial “every asbestos fiber is causative” theory of liability. The court ruled that, in doing so, the district court had failed to fulfill its gatekeeper function under Daubert v. Merrell Dow Pharmaceuticals, Inc., 509 U.S. 579 (1993), by admitting testimony without making the required Daubert findings as to relevance and reliability, and had erred by allowing the jury to make those determinations. Inasmuch as evidence was improperly admitted, the appellate court proceeded to conduct a harmless error review, which begins with a presumption of prejudice that can be rebutted by the party that offered the evidence showing that it is more probable than not that the jury would have reached the same verdict even if the improper evidence had not been admitted. Further, where, as here, the district court failed to exercise its gatekeeper function, the appellate court may review the record and determine for itself whether expert testimony satisfies the Daubert standard for relevance and reliability, if the record contains sufficient evidence to enable the court to make that determination. In this case, however, the Ninth Circuit concluded that the district court had not built a sufficient record for the Ninth Circuit to make this determination and thus remanded the case for a new trial. This holding reversed an earlier ruling to the contrary in Mukhtar v. California State University, 299 F.3d 1053 (9th Cir. 2002), amended by 319 F.3d 1073 (9th Cir. 2003).