Opinions — Thursday, August 6, 2026

The Ninth Circuit reversed the district court's grant of summary judgment to defendant Marron Lawyers, APC on plaintiff Koi Design LLC's California state-law claims for legal malpractice, breach of fiduciary duty, and negligent supervision. Koi alleged that Marron's associate, A. Douglas Mastroianni, grossly mishandled trademark infringement litigation between Koi and Strategic Partners, Inc., ultimately leading to default judgment, treble damages, and Koi's bankruptcy. The court held that genuine disputes of material fact existed on both the breach and causation elements of Koi's claims. On breach, the court concluded a reasonable jury could find Marron violated its duty to disclose material facts and significant developments in the SPI litigation—including that Mastroianni posed documented malpractice risks—and its duty to adequately supervise employees, including enforcing internal policies requiring paralegals on CM/ECF accounts. On causation, applying California's but-for test (which the court held subsumed the substantial-factor inquiry on these facts), the court found a reasonable jury could conclude that with competent counsel, Koi would have obtained a more favorable judgment, particularly because the default judgment resulted in part from Mastroianni's misconduct while at Marron, and that Koi would have replaced Mastroianni had it known of his incompetence, given that Koi immediately terminated him upon discovering the default.

The decision's significance lies in its application of California professional-conduct rules to establish both duty and breach in legal-malpractice and fiduciary-duty claims, treating violations of the Rules of Professional Conduct as dispositive evidence of breach. The court drew directly on Mastroianni's failure to comply with then-applicable Rule 3-500 (duty to keep clients reasonably informed of significant developments) and Rule 3-110 (duty to supervise subordinate attorneys) to support Koi's breach showing. On causation, the court rejected the argument that Mastroianni's post-termination misconduct at another firm broke the causal chain, holding that a jury could find Marron's failure to disclose material information prevented Koi from replacing Mastroianni earlier, and that the ultimate sanctions flowed partly from conduct during Marron's representation. Judge Gilman dissented on causation, concluding Koi failed to raise a genuine issue on but-for causation or that Marron's conduct was a concurrent independent cause for the malpractice and negligent-supervision claims, though agreeing a factual dispute existed on causation for the fiduciary-duty claim.

The Federal Circuit affirmed the PTAB's final written decision holding claim 1 of U.S. Patent No. 9,354,015 unpatentable as anticipated. The patent, owned by Ravin Crossbows, relates to crossbows with rotatable string guides, and the dispute centered on whether the Board properly construed "mounted to" to mean "connected to, either directly or indirectly." Ravin argued for a narrower construction—"physically connected to allow only rotation about a fixed axis"—contending the Board's construction was overbroad and conflicted with the specification's teachings.

The court applied de novo review to the claim construction and rejected Ravin's proposed construction on the ground that it would render superfluous claim 1's separate recitation that the string guides are "rotatable around" an axis. The court emphasized that claim terms should not be construed to make other limitations void or meaningless, and found that the functional and structural language elsewhere in the claim—particularly the requirement that the string guides rotate and apply force to the bow limbs—adequately bounded the scope of "mounted to." The court also declined to fault the Board for departing from a related district court's determination that "mounted to" carries its plain and ordinary meaning, holding that the Board could adopt its own construction after considering the district court's assessment under 37 C.F.R. § 42.100(b).