Google and Microsoft have been tangled in a high-profile legal dispute, and the search giant has now taken a large blow.

A federal judge has invalidated 13 Motorola patent claims against Microsoft. The claims cover a total of three patents that relate to a video coding standard. Microsoft had requested the court to invalidate those claims based on a patent law, and the court ultimately sided with the Redmond company.

Judge James L. Lobart, the presiding judge over the case, laid down the decision on Thursday, Feb. 7, in Microsoft's home state of Washington. The patents in question were 7,310,374; 7,310,375 and 7,310,376.

For the first patent in the series, the judge dismissed claims 14 through 18. Concerning the second patent, claims 13, 14 and 16 were invalidated, while the last patent saw claims 14, 15, 18 through 20 and 30 tossed out.

Meanwhile, the claims that remain standing are 8 through 13 for the first patent, claims 6 through 11 and 17 for the second patent, and claims 22, 23 and 26 through 28 for the third patent.

Not even the claims that remain standing are safe, however, as the court could still decide to invalidate them at any time in the future. The ruling dealt a serious blow to Google, and the invalidation was for "indefiniteness of means-plus-function," according to FOSS Patents.

"Even were a person of ordinary skill in the art able to devise an algorithm for decoding the function from the disclosed encoding description, that alone does not rescue the disputed means limitations from indefiniteness ...The specification needs to provide a decoding algorithm from which to base the understanding of one skilled in the art, and the court can find no such algorithm within the specification," explained Judge Robart.

In other words, Motorola's patents were not specific enough regarding the computer code involved. The judge's ruling has significantly narrowed the case, leaving Google's Motorola with only a few claims standing.

If the remaining claims remain valid, Microsoft would likely have to pay a reasonable rate to license what is deemed as a "standards-essential" technology, noted FOSS Patent's intellectual property specialist Florian Mueller.

The 13-02-07 Microsoft v Motorola Partial Summary Judgment is available at this link.