A lawyer for the film industry told the Supreme Court yesterday that millions of Americans, aided and abetted by the makers of Betamax, are in effect practicing tape "piracy" by regularly copying television programs on videotape recorders.

Stephen A. Kroft, arguing on behalf of Universal City Studios and Walt Disney Productions, asked the court to hold the Sony Corp., manufacturer of Betamax, responsible for what he depicted as a living-room crime wave that has "infected" the country.

The oral arguments in Sony Corp. of America vs. Universal City Studios Inc. et al. continued a massive battle between the two industries that began when the studios sued Sony in California, contending that each time a viewer copied one of their movies the federal law prohibiting infringement of copyrights was being broken.

The target of the suit was not the home taper but Sony. The most discussed remedy proposed was not to send FBI agents into private homes or to ban home recording, but to impose a licensing fee on Betamax sales to compensate the film makers.

In October, 1981, the Ninth U.S. Circuit Court of Appeals ruled against Sony, setting off expensive Capitol Hill lobbying on both sides, a public relations extravaganza and the Supreme Court appeal, accompanied by more "friend-of-the-court" briefs than in any other case on the court's docket, including abortion and reverse discrimination.

While its outcome will affect only Sony immediately, other manufacturers of video recorders, the publishing industry, the recording industry, the companies that manufacture tapes, the retail outlets that sell tapes and tape recorders, the advertising industry and 17 states have claimed a substantial interest in the case.

"The technology makes the case more interesting," Kroft told the justices. "But all this case really involves is unauthorized copying of motion pictures. That has never been permitted by copyright laws, and the fact that it is being done at home makes no difference.

"There are property rights involved here," he said. "We are not talking about something that has no value . . . . What we are talking about is an end result that is no different than tape piracy. We are not saying that these people are pirates, but millions of copies are being made and the end result is the same."

Dean C. Dunlavey, representing Sony, predicted that, if the court agreed with Universal and Walt Disney, "5 million-plus videotape recorder owners will be at the mercy of any copyright owner who seeks to take advantage of them."

He told the court that only a small percentage of television programming is copyrighted formally and that copying it is "fair use" of broadcast programs, exempt by law from copyright infringement charges.

"These people have put their programs on the air for people to receive. They should have no objection" to the use being made of them, he said.

But he consumed most of his half hour arguing that whether or not home tapers are lawbreakers Sony is not responsible for their actions. He said the recorders can be used for numerous purposes that are not illegal and that it was not Sony's intention that they be used illegally. In addition, he said, Sony has no way of knowing what owners are doing with their machines.

"Sony has put a warning in each recorder that it should not be used for copyright infringement," Dunlavey noted.

The case focuses primarily on "time shifting," recording programs for later viewing. And it is not the viewing itself that is under attack, but the copying.

The justices are expected to rule by summer. Whatever the outcome, the fight will continue in Congress for amendments to the copyright laws designed to undo what the court decides.