A Delaware federal judge on Feb. 16 invalidated a patent held by D&M Holdings Inc. as the company continues to face off against rival wireless speaker-maker Sonos Inc. in a protracted infringement fight.

U.S. District Judge Richard G. Andrews of the District of Delaware said in a 13-page memorandum opinion that plaintiff D&M's patent was directed to an abstract idea and thus was not patent eligible. Nothing in the patent claimed an inventive concept that would make it valid under U.S. patent law, he said, reviewing the case under the U.S. Supreme Court's Alice framework.

“I agree with defendant that this claim is, at most, directed to the automation of a process that can be (and has been) performed by humans,” Andrews wrote.

The ruling provides a boost to Santa Barbara, California-based Sonos, as it defends against D&M's claims that Sonos' multiroom wireless audio system infringes three of its patents. And it comes just two months after a federal jury found D&M-controlled Denon Electronics infringed three of Sonos' audio-control patents with its HEOS wireless speaker line.

The jury in that case awarded Sonos $2 million in damages and royalties.

D&M asserted counterclaims against Sonos in March 2016, accusing its competitor of infringing three of its own patents. That case was severed from the first suit, and the sides argued motions for summary judgment Jan. 30.

Andrews' decision only implicated one of the patents—identified in the opinion as the '899 patent.

D&M had argued Sonos “mischaracterized” its claimed invention as an abstract idea. According to D&M, its audio technology involved implementing a complex surround sound configuration that could not be done by a human.

Sonos, however, called D&M's product a “mere automation” of a well-known manual process of choosing playback without setting preferences. The features D&M touted were simply settings that any person can set manually, the company said.

On Feb. 16, Andrews sided with Sonos, saying there was nothing to indicate D&M actually improved computer functionality or identified an inventive concept in its patent application.

“Here, none of the independent or dependent claim language captures the 'sophisticated computer programming' or the 'user interface' that plaintiffs argue provide inventive concepts that were not well-understood, routine or conventional,” he said.

“Accordingly, there is no genuine dispute of material fact as to 'whether a claim element or combination of elements is well-understood, routine and conventional.”

Sonos is represented by George I. Lee, Sean M. Sullivan, Rory P. Shea, J. Dan Smith, Michael P. Boyea, Cole B. Richter and Jae Y. Pak of Lee Sullivan Shea & Smith and Philip A. Rovner and Jonathan A. Choa of Potter Anderson & Corroon.

D&M is represented by John M. Jackson, Matthew C. Acosta, Blake T. Dietrich, Christopher J. Rourk, Robert P. Latham, David Folsom and Wasif Qureshi of Jackson Walker and Jack B. Blumenfeld and Michael J. Flynn of Morris, Nichols, Arsht & Tunnell.

The case is captioned D&M Holdings v. Sonos.