The US Court of Appeals for the Federal Circuit reversed a district court’s decision upholding patent validity, finding that the subject patent’s specification clearly established that the written description failed to adequately support the full scope of the asserted claims (35 U.S.C. § 112). Mondis Technology Ltd. v. LG Electronics Inc., Case Nos. 23-2117; -2116 (Fed. Cir. Aug. 8, 2025) (Taranto, Clevenger, Hughes, JJ.)

Mondis sued LG for alleged infringement of a patent related to computer display technology. During prosecution, Mondis amended the claims to overcome prior art, changing a limitation from identifying a particular display unit to identifying a type of display unit (the type limitation). A jury found in favor of Mondis and awarded $45 million in damages. LG moved for judgment as a matter of law (JMOL), arguing that the patent was invalid due to a lack of written description supporting the type limitation. The district court denied the motion but granted a retrial on damages. The second jury awarded more than $14 million. LG appealed.

The Federal Circuit applied regional law standard (here, Third Circuit law) to review the district court’s denial of JMOL (i.e., assessing whether a reasonable jury could have reached the verdict). In evaluating patent validity under the written description requirement of § 112, the Court focused on whether the specification sufficiently demonstrated that the inventor possessed the claimed invention, including any amendments made during prosecution.

The Federal Circuit examined whether substantial evidence supported the jury’s finding of validity and concluded that LG did not need extrinsic evidence to challenge the patent’s validity but properly relied on the specification. The Court found that Mondis’ attempt to piece together fragments of testimony (primarily related to infringement) to argue for implicit support in the specification was insufficient because the specification’s plain language supported only the original unamended claim limitation, not the amended type limitation.

The Federal Circuit acknowledged that both parties presented expert testimony at trial. However, the Court found that even Mondis’ expert testimony, when considered alongside the specification’s plain meaning, failed to provide adequate support for the jury’s finding. While a jury may infer implicit support, Mondis did not present enough particularized testimony to justify such an inference.

Mondis also argued that the examiner’s allowance of the amended claim indicated sufficient support in the specification, and that the presumption of validity of an issued patent supported its position. The Federal Circuit rejected this argument, noting that the examiner’s focus was on overcoming prior art, not on evaluating written descriptions. Accepting Mondis’ position would effectively shield most patents from later invalidation, a result the Court deemed impractical.

Accordingly, the Federal Circuit reversed the district court’s ruling and found the asserted claims invalid for lack of written description.