The US Court of Appeals for the Ninth Circuit is expected to arrive at a decision today that could have drastic implications for Napster the maverick music-swapping service.

Napster is in the midst of a lengthy legal battle against some of the largest record labels, represented by the Recording Industry Association of America (RIAA).

The music powerhouses claim that Napster's service infringes on their copyrights by encouraging users to freely exchange their MP3 music files.

Napster claims it is merely providing the technological means for activities that are carried out by its users.

A three-judge panel heard arguments from both sides in October and, come Monday, will issue a decision that could either shut Napster down until the case has gone to trial or allow Napster to continue its operations.

Federal Court Judge Marilyn Hall Patel had already ordered Napster to shut down pending the outcome of the trial.

The appeals court overturned that decision in favour of holding the hearing last October to review the merits of each side's case.

The triumvirate of judges have a technology-friendly reputation, which has some legal experts doubting that the preliminary injunction against Napster will be reinstated. Others think the judges will send the matter back to Judge Patel.

"Most legal experts expect the decision to be handed back to the court for further review," said Malcolm Maclachlan, an Internet media analyst with IDC.

Maclachlan said Napster has 57 million users, according to the most recent estimates. "I don't really buy that though because I am three of them," he quipped, meaning he has three registered user names.

If Napster is ordered to shut down until trial, the pressure will be on for the company to maintain its user base until it can begin profiting from a fee-based service that the company said recently it will launch in June.

If it can hold onto just one percent of its 57 million users and collect US$5 from each of them with its fee-based service, the company would still be a big success, Maclachlan said.