Alcatel-Lucent, the French telecoms equipment maker, will appeal a decision by a US federal judge to overturn a $1.5 billion (£740 million) fine imposed on Microsoft in March for infringing on two patents.

The original fine, imposed six months ago, was the largest ever handed down by a US jury in a patent infringement case. The ruling could yet have an effect on the wider digital music market, analysts said.

Reacting to the judgment, the French company said that it believes it has a “solid case”, underlining that the jury in the original hearing had unanimously voted in favour of the fine against Microsoft.

Alcatel-Lucent said in a statement: “This reversal of the judge’s own pre-trial and post-trial rulings is shocking and disturbing, especially since — after a three-week trial and four days of careful deliberation — the jury unanimously agreed with us, and we believe their decision should stand."

The case centred on MP3 audio technology used in the Windows Media Player software. Alcatel-Lucent argued that technology used to encode and decode digital audio files in Media Player infringed on two of its patents.

In a ruling delivered yesterday, US District Court Judge Rudi M Brewster in San Diego said Microsoft had not infringed one of the two patents in question.

He added that the second patent is owned by both Alcatel-Lucent and Fraunhofer Gesellschaft, a German organisation that Microsoft paid $16 million to for the right to use the technology.

Fraunhofer was jointly responsible for developing the technology along with AT&T, which later disposed of Lucent, and was subsequently bought by Alcatel.

As Fraunhofer has not taken action against Microsoft, Microsoft did not have a case to answer to, the judge said.

Brad Smith, Microsoft’s general counsel, said that the verdict was “a victory for consumers of digital music and a triumph for common sense in the patent system.”

The appeal is likely to involve the original case being heard again at the district court level.

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