The way the Justice Department sees it, a controversial recent court ruling promises to shield corruption on Capitol Hill from successful attack.

The ruling would make effective bribery prosecutions of present or former members of Congress "virtually impossible in a large number of cases," says Solicitor General Wade H. McCree Jr.

The case involves an indictment of fromer representative Henry Helstodki (D-N.J.), a member of the House from 1965 to 1977. He has not yet gone to trial.

McCree wants the Supreme Court to review the ruling handed down in April by the 3rd U.S. Circuit Court of Appeals. For entirely different reasons, so does Helstoski. As seen by his lawyer, Morton Stavis, the ruling threatens the separation of powers among the branches of government.

It let "the executive [branch] use the grand jury unconstitutionally to obtain an unconstitutional indictment," Stavis charged. It also let the executive "intrude upon legislative immunity, and to publicize the offensive indictment" so as to defeat Helstoski at the polls, he said.

At the heart of the case is the provision of the Consitution that makes representatives and senators immune from prosecution when legislating or when within what the courts call the "sphere of legitimate legislative activity." The Constitution's language is, "for any speech in either house, they shall not be questioned in any other place."

The Helstoski indictment grew out of a long series of federal investigations in New Jersey into so-called "private" immigration bills with which a member of Congress seeks the admission of particular individuals into the United States. Nearly always, Congress passes such bills routinely.

In 1975, the investigations resulted in the indictment and conviction of former Helstoski aide Albert DeFalco for having fraudulently represented himself as working for the congressman when he took money for the introduction of private bills by Helstoski. The prosecution stipulated on the record that Helstoski, a defense witness, wasn't in on the conspiracy.

Meanwhile, over a 25-month period starting in 1974, Helstocki voluntarily appeared 10 times before eight grand juries around the state. He testified in detail about why he'd introduced the bills, how he presented them in the House, the processing by his office of requests for private bills, and his own purported inquiries into allegations of bribery and fraud in connection with the bills. He also produced voluminous records.

Before each grand jury appearance, the government advised Helstoski that he could invoke the constitutional privilege against self-incrimination and that he was not required to produce documents. In reply, he said he wouldn't invoke the privilege "under any circumstances" and pledged his "full cooperation."

In June 1976 a grand jury before which Helstoski hadn't appeared indicted him and his congressional staff. In the primary election a week later, he was defeated.

The indictment accused Helstoski and the aides, in four counts, of having conspired to accept and of accepting bribes to introduce immigration bills in behalf of specified aliens residing illegally in the United States. He flatly denies having received any bribe.

Helstoski sought dismissal of the indictment on several grounds, each relating to the speech-or-debate clause immunity.

First, he contended that the grand jury impermissibly heard evidence on legislative acts -- his introduction of the private bills. U.S. District Court Judge H. Curtis Meanor termed the contention "untenable" termed the conntention "untenable" because courts "simply will not go behind the face of an indictment... to test the competency of the evidence" on which it was based. The appeals court agreed.

Second, Helstoski said that the indictment referred explicitly to legislative acts and therefore was invalid. Meanor, again upheld by the 3rd Circuit, disagreed. To show that Helstoski committed bribery, he said, an inquiry into his legislative performance "is not essential..."

Third, in a claim of central importance to members of Congress and prosecutors, Helstoski said he hadn't waived his immunity either by his voluntary grannd jury appearances or by his failure to assert the speech-or-debate privilege until near the end of the investigation.

Without deciding whether he, rather than the House, was empowered to waive the privilege, as claimed by the government, the lower courts upheld him.

Even if Helstoski could waive immunity, Chief Judge Collins J. Seitz wrote for the 3rd Circuit, a waiver would have to be "express and for the specific purpose for which the evidence of legislative acts is sought to be used against the member."... He added, "We find no such waiver."

Fourth, Helstoski argued that if he were brought to trial, his immunity would prevent the government from using his private bills and other evidence of the performance of his legislative acts to try to convict him of bribery.

This point was accepted by Meanor as "beyond dispute." But the appeals court went further: it held that speech-or-debate bars the government from introducing evidence at trial if it contains any "reference to past legislative acts."

This "very expansive view... would bar virtually all evidence of relevant events occurring subsequent to the performance of a legislative act" and would "render effective bribery prosecutions of present or former members of Congress virtually impossible in a large proportion of cases," McCree said in his pettion for Supreme Court review.

The prosecution would be "precluded not only from proving the actual performance of a legislative act, but also from introducing any evidence that refers to the past performance of a legislative act," he continued.

With substantial portions of the government's proof barred, the result would be "arbitrary protection for corrupt legislators who are lucky enough (or shrewd enough) to structure their participation in the bribery scheme so that their conversations occur after the legislative performance," McCree contended.

By contrast, Stavis, urging dismissal of the indictment, told the high court that the government, without actually saying so, was seeking from it a decision that would take from Congress the constitutional power to judge the conduct of its members. This would undermine congressional independence and upset the "reasonable bal ance" the court has struck in prior cases "between the speech-or-debate clause and the proper functioning of our criminal justice system," he argued.

"The picture which emerges in this case is not a pretty one and does not speak well of the respect of the executive branch... for the principle of legislative independence," Stavis said.

The 3rd Circuit ruling on waivers was denounced by McCree as being "virtually unparalleled in stringency elsewhere in the law." As a practical matter, it could wipe out the possibillity of waivers, he said.

But Stavis accused the government of omitting to say that Helstoski, in appearing before the grand juries, "had every reason at the time to believe that it was his erstwhile aide pursuing.... At no time was [Helstoski] ever notified that he was a target." For the government to argue "that there was a waiver of a great constitutional principle seems absurd," he said.

Stavis also said that the investigation, led by then U.S. attorney for New Jersey Jonathan L. Goldstein, "was instigated by the congressman himself when he heard urmors of corruption."

Moreover, the lawyer charged, Gold stein "engaged in a massive program of leaks to the press" before producing an indictment a week before the primary, and is relying on witnesses "beholdenn" to him "because of deep involvement in criminal actiies: ."