Koi Design LLC v. Marron Lawyers, APC

Koi Design · United States Court of Appeals for the Ninth Circuit · August 6, 2026 · No. 23-55704

Summary

The Ninth Circuit reversed the district court's grant of summary judgment in favor of a law firm in a legal malpractice and breach of fiduciary duty action brought by a former client. The panel held that genuine disputes of material fact existed regarding whether the firm breached its duties to disclose information and supervise an incompetent associate, as well as whether the firm's conduct caused the client's damages. The court also concluded that the district court did not violate Federal Rule of Civil Procedure 56(f)(2) by granting summary judgment on grounds not explicitly raised by the parties, as the record provided adequate notice. The case was remanded for further proceedings consistent with the opinion.

Court
United States Court of Appeals for the Ninth Circuit
Writing for the Court
Lucy H. Koh; Ronald Lee Gilman; Kim McLane Wardlaw
Jurisdiction
Federal
Decision date
August 6, 2026
Docket number
23-55704
Procedural posture
Koi Design LLC appealed the Central District of California's amended summary-judgment order granting Marron Lawyers, APC summary judgment on Koi's legal-malpractice, breach-of-fiduciary-duty, and negligent-supervision claims.
Standard of review
De novo review of a grant of summary judgment. Summary judgment is proper when, construing the facts and reasonable inferences in favor of the nonmoving party, there is no genuine dispute of material fact and the movant is entitled to judgment as a matter of law.
Precedential value
published and precedential
Parties
Koi Design LLC v. Marron Lawyers, APC
Disposition
reversed_and_remanded

Topics

summary judgmentprofessional negligencenegligent supervisioncivil procedurecommercial litigation

Practice areas

civil procedureprofessional negligencecommercial litigationtorts

Questions Presented

  1. Whether the district court violated Federal Rule of Civil Procedure 56(f)(2) by granting summary judgment on a ground or theory not raised by the parties without adequate notice and an opportunity to respond.
  2. Whether genuine disputes of material fact existed regarding Marron's breach of duties to disclose material facts and significant litigation developments and to adequately supervise Mastroianni.
  3. Whether genuine disputes of material fact existed regarding causation of Koi's injuries on its legal-malpractice, breach-of-fiduciary-duty, and negligent-supervision claims.
  4. Whether California's substantial-factor causation standard required application of the but-for test on the facts of this case.

Holdings

  1. The district court did not violate Federal Rule of Civil Procedure 56(f)(2) because Koi had adequate notice that causation, including whether Koi would have obtained a more favorable result in the underlying litigation, was a basis for summary judgment.
  2. Genuine disputes of material fact existed as to whether Marron breached its duties to disclose material facts and significant developments to Koi and to adequately supervise Mastroianni.
  3. Although California's substantial-factor test generally includes an exception for concurrent independent causes, the exception did not apply to Koi's causation theory because Mastroianni's and Marron's alleged misconduct were dependent causes operating in combination. The but-for causation test therefore applied to all of Koi's claims on the facts presented.
  4. Koi presented sufficient evidence for a reasonable jury to find that Marron's conduct was a cause in fact of Koi's injury and that Koi would have obtained a more favorable result in the SPI Litigation or obtained competent counsel but for Marron's conduct. Summary judgment on all three claims was therefore improper.

Key quotations

For the reasons stated below, we agree with Koi that there is a triable issue of fact as to both breach and causation. (22-23)
Because the substantial factor causation test requires us to apply the but for causation test in this case, we apply the but for causation test to all of Koi’s claims. (34-35)
There are genuine disputes of material facts as to whether Marron breached its duties to Koi and whether Marron’s conduct caused Koi harm. (49)

Factual background

Koi retained Marron to represent it in a trademark dispute and subsequent litigation brought by Strategic Partners, Inc. Marron's associate and lead attorney, A. Douglas Mastroianni, missed deadlines, failed to participate in required discovery procedures, failed to maintain proper electronic filing notifications, and continued mishandling the matter despite known performance and malpractice concerns. Marron did not disclose those concerns or significant litigation developments to Koi and did not adequately supervise Mastroianni. After Mastroianni continued representing Koi at another firm, the underlying litigation ended in terminating sanctions, default judgment, and treble damages, contributing to Koi's bankruptcy.

Procedural history

Koi sued Marron, A. Douglas Mastroianni, and Bloom Firm under California law based on alleged mishandling of Koi's trademark litigation. The district court initially granted summary judgment on the legal-malpractice claim, denied summary judgment on the breach-of-fiduciary-duty claim, and did not address negligent supervision. After Marron sought clarification and correction, the district court issued an amended order granting summary judgment on all three claims solely for lack of causation. The amended order merged into the final judgment, and Koi timely appealed.

Remand instructions

Remanded for further proceedings consistent with the opinion, including proceedings on Koi's legal-malpractice, breach-of-fiduciary-duty, and negligent-supervision claims.

Court Document

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