The US Supreme Court has refused to hear an appeal from the maker of the BlackBerry in the long-running battle over patents for the popular handheld e-mail device.

The decision may result in a trial judge granting an injunction that would force the company to shut down its service in the United States. The company seeking the injunction, NTP, has proposed that American BlackBerry users would have a 30-day grace period before the service was switched off.

Research in Motion (RIM), the Canadian company that makes the device, had asked the Supreme Court to review a ruling made by a lower court that the company had infringed the rights of NTP, a tiny patent-holding company based in Virginia.

A federal appeals court ruled that RIM had violated US patents even though its main relay station for e-mail and data transmission is located in Ontario, Canada. The company came under US jurisdiction because its customers use the BlackBerry within American borders, the court decided.

Since its introduction in 1999, the BlackBerry has revolutionised communications, allowing business travellers and government employees to send and receive e-mail outside their offices and away from their computers.

The dispute has resonated not only with private BlackBerry users who worry that their lifeline to their offices could be severed, but also with the American and Canadian governments.

Canadian officials are concerned that research and development in other industries will be stifled if RIM loses, while many American law enforcement and health workers rely on the BlackBerry for communicating in crisis situations.

The Canadian company had wanted the Supreme Court to rule on whether American patent law is technologically out of date in the age of the internet and the global marketplace.

Its refusal means that the case will return to a lower court, where NTP is expected to demand that an infringement shutting down the BlackBerry service is enforced.

A lawyer representing RIM, Herbert L. Fenster, said the company is fighting the injunction. He also said that federal law prohibits the from cutting off the BlackBerry service to federal, state and local government users, as well as others who rely on the devices to communicate during a public emergency.

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