The U.S. Supreme Court yesterday let stand the racketeering convictions of a Northern Virginia couple and the seizure of their three bookstores and nine video rental stores for selling obscene material.

In a boost for federal prosecutors' battle against pornography, the court refused to hear the case of Dennis E. and Barbara A. Pryba. The couple were convicted in 1987 of selling four obscene videotapes and six obscene magazines in the federal government's first use of the racketeering law to prosecute an obscenity case.

The law permits the forfeiture of property that is the "proceeds" of the racketeering activity. The jury, after finding the Prybas guilty, directed that the bookstores, video rental stores and other assets -- totaling more than $1 million -- be seized.

The 4th U.S. Circuit Court of Appeals in Richmond upheld the convictions and the forfeiture, ruling that the forfeiture provisions do not violate the First Amendment, even though some of the materials seized may not be obscene and would be entitled to constitutional protection in other circumstances.

Holding otherwise "would allow criminals to protect their loot by investing it in newspapers, magazines, radio and television stations," the court said.

The Prybas' lawyers argued that the use of obscenity as one of the crimes that can support a racketeering conviction "will seriously hinder, if not obliterate altogether, the viability of businesses which are presumptively protected under the First Amendment."

Noting that the obscene videotapes and magazines were worth a total of $105.30, they added: "To seek to eradicate obscenity by means of forfeiture is to make a conscious decision to permanently suppress books and movies, which are undeniably protected by the First Amendment."

The Justice Department argued that the forfeiture did not violate the First Amendment. It said the books and magazines were seized because they were the proceeds of illegal activity, not because of their content.

Justice Byron R. White dissented from the Supreme Court's decision not to hear the case. He said the court should use the case to decide whether the federal racketeering law requires that each defendant agree personally to commit two or more crimes covered under the statute, or whether the defendant may simply agree to the commission of the acts by another conspirator.

Dennis Pryba was sentenced to three years in prison and fined $75,000, while his wife was given three years' probation and fined $200,000. Educational Books Inc., the couple's primary business, was fined $100,000.

Barbara Pryba's sister, Jennifer G. Williams, whose conviction also was let stand yesterday, was given three years' probation.