When Fawn Hall testified that she shredded reams of secret White House documents last fall and then walked out of her office with incriminating classified papers stuffed inside her boots and dress, the Iran-contra affair entered a new phase of public consciousness.

After her sworn testimony, no one can ever claim credibly that this episode was merely a sad example of official good intentions gone awry. Nor can anyone argue convincingly that, however many mistakes were made, this was not a case of corruption.

Hall's testimony shredded those claims as surely as the shredder in her National Security Council office pulverized vital evidence last November. What has been revealed, by her and by others testifying in the last six weeks, is a White House scandal of historic proportions. In the scope of its lawlessness, it rivals the Teapot Dome scandals in the Harding administration and Watergate under Richard M. Nixon.

The Iran-contra affair stands exposed as a massive attempt at an official cover-up after lengthy and elaborate attempts to circumvent the spirit and letter of law and the expressed will of Congress over several years. When their illicit actions began to surface, U.S. officials lied, destroyed evidence, conspired to keep silent and thus obstructed justice.

From the highest levels of government, no one emerges from this story looking good. For example, the latest testimony detailing the desperate attempt to destroy evidence and to cover up inside the White House complex makes a mockery of claims by Attorney General Edwin Meese III last November after the scandal erupted. Despite published reports that documents had been shredded in Lt. Col. Oliver L. North's NSC office, Meese then cited no need to call in Federal Bureau of Investigation agents and secure evidence because no reason existed to suspect criminal actions.

Ironically, the witness whose actions seem most understandable is Hall, the loyal, dedicated young secretary. She, at least, committed her acts out of what she thought the best of motives -- to save admired higher-ups in whom she believed and to preserve a secret official policy that she also deeply believed to be in the country's best interests.

"I was very emotional at the time," she told congressional investigators Monday in explaining why she shredded documents and altered classified papers, "and I was concerned about protecting . . . the Iran initiative and the contra initiative."

The same cannot be said so easily about motivations of others who implicated in the affair.

A sordid story of greed and corruption has been spun before Congress and the public. Many of those who came before the select investigating congressional committees claimed that they acted out of purely patriotic motives. Now they have been tainted by hard evidence of profiteering. The desire to make big bucks is at the center of a tale characterized by great amounts of cash, much of which remains unaccounted for and which flowed secretly into many channels and pockets.

Sen. William S. Cohen (R-Maine), referring to accounts of dealing and double-dealing by administration officials and their operatives, put it best when he described the episode as "a story of betrayal."

It has also been a story of true believers, zealots with misguided notions of patriotism.

"I don't like people coming in here waving the flag and spitting on the Constitution," Senate select committee Vice Chairman Warren B. Rudman (R-N.H.) said in obvious disgust during a recent break in testimony.

Senate committee Chairman Daniel K. Inouye (D-Hawaii) memorably expressed another aspect, saying he has been disturbed by laughter that frequently greeted comments of some of the private/public operatives who testified about their roles as secret agents for the United States. To find, he said, in tones of utmost dignity, "an American lieutenant colonel, who everyone suggests is second only to the president of the United States, committing this country, its power and majesty, to defend Iran, without even consultation with the Congress of the United States, is just unbelievable . . . . I just hope the people of the United States realize this was not funny business. This was very tragic business."

That encapsulates the testimony. If the American people find this amusing, or acceptable, in the 200th anniversary year of the Constitution, then God help the Republic.