NOT FOR PUBLICATION

UNITED STATES COURT OF APPEALS

FOR THE NINTH CIRCUIT

TATIANA KOROLSHTEYN, on behalf of 

herself and all others similarly situated, 

Plaintiff-Appellant, 

 v. 

COSTCO WHOLESALE CORPORATION 

and NBTY, INC., 

Defendants-Appellees.

No. 17-56435 

D.C. No. 3:15-cv-00709-CAB 

MEMORANDUM*

Appeal from the United States District Court

for the Southern District of California

Cathy Ann Bencivengo, District Judge, Presiding

Argued and Submitted November 9, 2018

Submission Vacated November 13, 2018

Resubmitted February 20, 2019

Portland, Oregon

Before: TALLMAN and IKUTA, Circuit Judges, and BOUGH,** District Judge.

Tatiana Korolshteyn and other putative class action plaintiffs appeal an 

adverse summary judgment entered by the district court in favor of Costco 

 

* This disposition is not appropriate for publication and is not precedent

except as provided by Ninth Circuit Rule 36-3.

** The Honorable Stephen R. Bough, United States District Judge for the 

Western District of Missouri, sitting by designation.

FILED

MAR 7 2019

MOLLY C. DWYER, CLERK

U.S. COURT OF APPEALS
2 

Wholesale Corporation and NBTY and a denial of Daubert motions in a diversity 

class action. The class alleges that appellees violated California’s Unfair 

Competition Law (“UCL”) and Consumer Legal Remedies Act (“CLRA”) by 

falsely advertising the benefits of TruNature Ginkgo Biloba with Vinpocetine. 

Both parties had introduced expert testimony supporting their respective claims

and the district court denied appellants’ Daubert motions to exclude the testimony 

of three of the appellees’ expert witnesses. We have jurisdiction under 28 U.S.C. 

§ 1291. We review summary judgment de novo. See Edwards v. Wells Fargo & 

Co., 606 F.3d 555, 557 (9th Cir. 2010). We review a district court’s admission of 

scientific evidence for abuse of discretion. See Gen. Elec. Co. v. Joiner, 522 U.S. 

136, 146 (1997). Because the district court did not have the benefit of a recently 

released decision of our court, we reverse the district court’s grant of summary 

judgment, affirm the denial of the Daubert motions, and remand for further 

proceedings.

1

 

Based on the recently released opinion, the district court erred in granting 

summary judgment by failing to apply the appropriate substantive evidentiary 

standard of a preponderance to claims brought under California’s consumer 

 

1 The motion to file and request to extend time for filing an Amicus Curiae by the 

Consumer Attorneys of California in support of appellants is denied as moot 

following the panel’s reversal of summary judgment and the Court’s recent 

decision in Sonner v. Schwabe N. Am., Inc., 911 F.3d 989 (9th Cir. 2018) 

confirming the appropriate standard of proof in UCL and CLRA claims. 
3 

protection laws. See Sonner v. Schwabe N. Am., Inc., 911 F.3d 989, 992 (9th Cir. 

2018). The appropriate evidentiary standard must be applied in determining 

whether a factual dispute must be submitted to a jury. See Anderson v. Liberty 

Lobby, Inc., 477 U.S. 242, 255 (1986). The district court applied a tougher, 

conclusive standard, holding that the existence of scientific studies supporting the 

alleged benefits of the product precluded the appellants from conclusively proving 

falsity in the appellees’ product labeling. We therefore remand so that the district 

court may apply the newly clarified standard. See Sonner at 992.

The district court did not abuse its discretion in denying appellants’ Daubert 

motions and admitting the testimony of appellees’ expert witnesses. Concerns 

regarding the admission of “shaky” evidence are resolved through the trial process 

through “[v]igorous cross-examination, presentation of contrary evidence, and 

careful instruction on the burden of proof.” Daubert v. Merrell Dow Pharm., Inc., 

509 U.S. 579, 596 (1993). We affirm the district court’s denial of appellants’ 

Daubert motions. 

REVERSED IN PART, AFFIRMED IN PART, and REMANDED. 

Each party shall bear its own costs on appeal.