This tale, perhaps apocryphal, is one that CIA officers still tell with glee

It's the mid-1950s, and two elderly lawmakers sit in a Senate subcommittee hearing room, listening to the CIA's deputy director of operations drone through his prepared statement on the agency's latest covert action. One of the senators rests his head in his arms and falls asleep. His colleague stares blankly at the briefer, stealing glances at a newspaper.

The CIA official raises his voice for a moment, more to relieve his own boredom than to stir his audience. “Paramilitary activities,” he intones, “have been an important part of our programme since the early days of the Cold War.”

The slumbering senator awakens with a start. “Parliamentary activities?” he bellows. “You fellas can't go messin' round with parliaments. I won't have it!” With that, the octogenarian rose and left the room.

The moral of the story is evident not only did the CIA's legislative watchdog have no teeth, it was sound asleep.

Attorney-General Eric Holder's appointment last week of a special prosecutor to investigate CIA prisoner abuses is but the latest of many efforts to rein in the agency. I've been a witness to some of those efforts, as an assistant to Sen Frank Church of Idaho during his committee's investigations in the 1970s and later as an aide to former defence secretary Les Aspin when he led a probe of agency structures in the aftermath of the Aldrich Ames spying scandal.

Such inquiries can prove useful, leading to critical reforms, stronger oversight and, perhaps most important, changed attitudes about the CIA and other intelligence agencies. But I've also learned that high-profile investigations will not transform human nature, turning intelligence officials - or the presidents and White House aides who direct them - into angels, unsusceptible to zeal and folly. Even when the watchdogs on Capitol Hill or in the Justice Department awaken, intelligence abuses and scandals will recur.

We will launch new investigations and introduce new reforms, but sometimes all we can do is clean up the messes after the fact. So let's get used to it.

During the first half of the Cold War, the CIA was largely free of serious congressional supervision. And despite controversies such as the U2 shoot-down over the Soviet Union, the Bay of Pigs fiasco and the covert funding of the National Student Association, the agency escaped widespread public opprobrium. That changed in 1974, when the New York Times's Seymour Hersh reported that the CIA had deployed its dark arts at home, spying on American citizens. In response, Senate leaders tapped Church to lead the first major investigation of the CIA.

The Church Committee discovered that intelligence abuses ran far deeper than initially reported. The CIA had indeed spied on Vietnam War dissenters at home, but the FBI had gone further, disrupting the lives of antiwar protesters and civil rights activists. It was “a road map to the destruction of American democracy,” committee member Walter Mondale said during a public hearing.

Church was equally appalled by the overseas excesses of the CIA, including covert actions against democratic regimes - such as Chile's - and assassination plots. He blasted the agency for “the fantasy that it lay within our power to control other countries through the covert manipulation of their affairs.”

At the time, Church told me that when he first came to the Senate in 1957, “some of those senior senators who did have this so-called (CIA) watchdog committee were known to say, in effect 'We don't watch the dog. We don't know what's going on, and furthermore, we don't want to know.' “He vowed to take a new approach but found it difficult to learn exactly who told the CIA to do what - a dilemma the nation faces today in trying to understand who ordered secret prisons, harsh interrogations and extraordinary renditions.

After one of our closed sessions on CIA assassination plots, Church leaned back in his chair and rubbed his forehead in frustration. Who had ordered the plots against Patrice Lumumba of Congo and Fidel Castro of Cuba? The president? The director of central intelligence? Someone lower down in the CIA? The testimony from the agency's witnesses was filled with ambiguities. “ 'Could,' 'would,' 'probably,' 'assume,' 'might,' 'have a feeling,' “ Church fumed to a particularly evasive (or forgetful) witness. “And we're talking about a matter of such grave importance as assassination!” The committee was never able to pinpoint responsibility.

In the wake of the Church Committee inquiry, the majority of lawmakers agreed that sleeping watchdogs were no longer acceptable. Congress established Senate and House intelligence committees; passed the Foreign Intelligence Surveillance Act to rein in the National Security Agency and created stronger reporting requirements to keep lawmakers on the two committees informed of important intelligence activities. A new era of accountability had dawned in Washington.

Or so we thought.

Within a decade, the Iran-Contra scandal revealed more misdeeds, when the Reagan administration and elements of the CIA bypassed oversight procedures to conduct covert actions in the Middle East and in Nicaragua. After another investigation, Congress adopted additional oversight mechanisms and strengthened the CIA's office of inspector general.

Then, in 1994, the CIA found itself again on the front pages when it was discovered that a Soviet mole, Aldrich Ames, had effectively dismantled the agency's spy ring in Moscow. President Bill Clinton appointed Aspin, a former defence secretary and congressman from Wisconsin, to head an inquiry into this treason.

The commission looked not just at the Ames debacle but at how well the intelligence agencies were adapting to the post-Cold War world. During the inquiry, Aspin told me about a conversation he'd had with former intelligence chief William Colby. He asked Colby about what happened during the early 1970s when members of the congressional oversight committees objected to a CIA operation. “Colby was stunned,” Aspin remembered. “The question had never come up before. The committees preferred not to get involved.”

Aspin was determined to scrutinise the nation's intelligence activities in 1995, but tragically, he died during the inquiry. His replacement, former defence secretary Harold Brown, followed Aspin's agenda, and the commission presented in 1996 several useful (if unheralded) reforms it tightened counterintelligence procedures to reduce the chances of another Ames emerging and, since treason can never be eradicated, to ensure that a future Ames would be detected more quickly.

With such midcourse corrections - from the Church Committee, the Iran-Contra investigators and the Aspin-Brown Commission - US intelligence officers appeared to grow aware of their legal and ethical boundaries and their new and (supposedly) improved oversight from the Hill. But Sept 11, 2001, changed all that. In the crucible of fear that followed, the safeguards we'd so painstakingly fashioned over the years fell apart. Following directives from the Bush White House and the Justice Department, the CIA ratcheted up its counterterrorism methods, leading to the secret prisons abroad, the kidnapping of terrorism suspects, the use of torture - and yet another major scandal when these approaches came to public attention.

Perhaps we should have seen it coming.

We can despair that misdeeds will continue to occur, or we can acknowledge human foibles and overreactions and take steps to lessen their impact. The starting place, of course, is to ensure that accountability is vigorously exercised - by true watchdogs who attend oversight hearings, ask tough questions, examine budgets closely and reject whispered briefings to a Gang of Eight or a Gang of Four when the law envisions briefings to the full intelligence committees. These bodies have demonstrated that they can be truste d with the nation's secrets.

But even with improved oversight, human nature decrees that things will go wrong. Often with the best of intentions, and caught up in anger or fear, an administration will order questionable operations such as warrantless wiretaps; or an overzealous CIA officer will waterboard a detainee 183 times. The president who brought us the CIA in 1947, Harry S. Truman, understood that oversight - though important - would not be enough. “You see, the way a free government works,” he said, “there's got to be a housecleaning every now and then.”

That is why Holder's appointment of a federal prosecutor, John Durham, to examine the charges of CIA prisoner abuse is the right call. A special prosecutor can help the nation understand the legal issues at stake and begin bringing to justice those who ignored the rules for interrogations. But a true housecleaning also requires a special commission to explore the broader ethical and foreign policy questions that emerged from the scandal, as well as examine the broader litany of offences - and lines of responsibility - that took the fight against terrorism off track, transforming it into a war against America's own ideals.

As with the Church and the Aspin-Brown reforms, success will depend on the willingness of elected officials in the executive and legislative branches to maintain a closer watch over the secret agencies. As another wise president, Thomas Jefferson, understood, vigilance is the price of liberty - an axiom still valid today.—Dawn/LA Times-Washington Post News Service

Loch K. Johnson, a professor of international affairs at the University of Georgia, is the editor of the Intelligence and National Security journal and the author of “New Storms on the Horizon America's Search for Security After the Cold War.”