But those notions provoked skepticism and sharp questioning from several justices, who wondered how inventors could know whether many people might use their products for illicit purposes.
"How do we know in advance on your test" whether the inventor is safe to go forward? asked Justice David H. Souter.

Michael Petricone of the Consumer Electronic Association, left, confronts Rick Carnes, president of the Songwriters Guild.
(Dennis Brack -- Bloomberg News)
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washingtonpost.com's David McGuire reports from the Supreme Court that the justices engaged in a lively debate with attorneys for the recording industry and Grokster/StreamCast over whether this case hinges on a 1984 ruling involving the home video recorder. (March 29, 2005)
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Justice Antonin Scalia said that an inventor has to know what his liability would be from the beginning. "I'm a new inventor," Scalia said. "I'm going to get sued right away."
Scalia and Souter asked whether other popular technologies, such as the Xerox copying machine or Apple Computer's iPod music player, would have seen the light of day given that they can and are used for illegal purposes.
And even if an inventor knows there might be illegal use, asked Justice Anthony Kennedy, how much is too much?
Justice Stephen G. Breyer noted that there are "excellent uses" of file-sharing technology, including by libraries and other institutions that transfer documents that are not copyrighted. Some music bands also allow their songs to be traded for free.
But the justices expressed discomfort with the notion that if they uphold the ruling of the Court of Appeals for the 9th Circuit Grokster and Streamcast Networks would walk away scot-free.
Breyer and O'Connor asked whether the case could be sent back to lower courts for a trial on whether Grokster and Streamcast networks deliberately induced users to steal songs and videos, which would be illegal under existing copyright law. The lower courts largely sidestepped those issues.
That is the outcome preferred by several major technology and telecommunications companies, such as Intel Corp., Microsoft Corp. and Verizon Communications Inc. which condemn Grokster but want the Sony precedent maintained.
But Verrilli argued that merely going after the Groksters of the world for encouraging infringement deprives the entertainment industry of being able to quickly seek to shut down businesses based primarily on illegal file sharing.
The case is MGM Studios v. Grokster Ltd., 04-480. A ruling in the case is expected by July.