Mercifully, that quaint notion of a free press keeps us going. Just as breadknife manufacturers are not held liable for the rare unlawful uses of their products, modern communications businesses are not shut down simply because they have the potential to enable others to break the law. It would be absurd to blame Vodafone for terrorists chatting across their network.

Yet if some of America’s biggest entertainment companies have their way, that presumption of a communication medium’s neutrality is about to disappear. Next Tuesday, the United States Supreme Court will begin hearing a case that affects anyone who has ever downloaded a music track, recorded a television show, or even sent an e-mail. The case, known as MGM v Grokster, is the culmination of a four-year legal battle to determine whether “peer to peer ” file-swapping services are liable for every pirated digital file that passes through their networks. The issues, to non-geeks, may appear arcane, but they affect the very future of technological innovation. They boil down to this: if a technology can potentially be used for ill, should it be banned — so preventing any of its legitimate uses?

The defendants are two American companies that make file-sharing software, Grokster and StreamCast Networks, known for a program called Morpheus. In 2001, a powerful alliance of entertainment companies brought a lawsuit claiming that these software companies should be held responsible for copyright breaches by their users. It was easy for the music industry to shut down Napster, as its technology required all exchanged digital files to pass through the comp any’s central computers. But with Morpheus and Grokster, there is no central infrastructure for the lawyers to target: the software simply lets users find files on each other’s computers.

In 2003, a federal judge ruled that the developers could not be held liable for how their users interact across peer-to-peer networks. The ruling was upheld the next year in California’s Ninth Circuit Court of Appeals. Now the movie and music industries, along with supporters ranging from the National Football League to the Church Music Publishers Association, are going for the big one. If they win, innovation will be the victim.

The complainants want to overturn the famous “Sony Betamax ruling” of 1984, which held that manufacturers of video recorders were not responsible for tape piracy involving their machines. At the time, the court, by a five-to-four majority, decided to protect any technology from liability if it was “merely capable” of “substantial, non-infringing use”. The decision freed manufacturers to develop many of today ’s must-have gadgets, from the iPod to personal video recorders, which may be used both for unlawful and “non-infringing” purposes. In the propaganda campaign that preceded the Betamax case, Jack Valenti, president of the Motion Picture Association of America, declared that the video recorder was “to the American film producer and the American public as the Boston strangler is to the woman home alone”. Strange, then, that video rentals went on to become the film industry’s main source of revenue.

Established interests have never much liked innovation. Back in 1906 the composer John Philip Sousa predicted “a marked deterioration” in musical tastes as newfangled gramophones “reduce the expression of music to a mathematical system of megaphones, wheels, cogs, disks, cylinders and all manner of revolving things”. Similar battles were fought over the printing press, photocopier, mechanical piano, radio and television. Remember how home taping was going to kill music a generation ago? Music seems to have survived.

Yes, most of the traffic flowing through the peer-to-peer networks involves breaches of copyright. And yes, music sales did fall by almost a quarter in the five years to 2003, as fans realised that technology offered a free alternative to extortionate CD prices. But the roughly 10 per cent of “legal” file-swapping on these networks allows programmers to swap code, academics to exchange learned papers and little-known musicians to gain a fan base. Why should the music industry be able to close such communications channels? Just because technology comes along and disrupts existing business models, should copyright owners not find clever ways to adapt, rather than suing 12-year-olds and fighting software developers in court?

If the studios do win, it will be the consumer who loses. The next generation of digital music players, internet telephony, TV recording equipment — all will suffer from a new legalistic caution that will stifle progress. The music lobby may have more star names on its side: a Sheryl Crow and a Brian Wilson for every Terence Trent D’Arby on the software companies’side. But if the music lobby wins, you might as well swap your iPod for a Thomas Edison wax cylinder.

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