FEW speeches made on the Senate floor have the impact their orators hope for. Dianne Feinstein’s speech on March 11th, in which she accused the CIA of hiding documents from and then bullying the Senate committee which oversees its activities, was an exception: it caused a storm. American spooks often claim that they are subject to far more oversight than their competitors in other countries and therefore ought to be trusted not to abuse their powers. This only holds if the overseers are allowed to do their job.

Accusing the CIA and NSA of being out of control is something of a political cliché, rather like accusing the president of acting unconstitutionally or Congress of being useless. But it is not one that Mrs Feinstein (pictured) has used before in her 21 years in the Senate, four of them as head of the committee on intelligence. Asked what she thought of Edward Snowden’s intelligence leaks on NBC’s Meet the Press, she responded that, “to glorify this act is really to set...a new level of dishonour”.

Overseers observed

At issue is the investigation by the intelligence committee of the CIA’s programme of rendition (snatching terrorist suspects and moving them from one country to another), detention and interrogation, which began in 2002. Barack Obama ended the programme five years ago, by which time much of it had ceased to operate. (The detention part, symbolised by Guantánamo Bay, has been harder to end). The president declined to order an investigation into what the CIA had been up to, but members of the oversight committee voted by 14-1 to conduct their own.

It has been a slow process: the investigation began in 2009. The CIA provided 6.2m pages of documents for the committee’s staff to sift through. Rather than allowing staff to carry this hoard off to their offices on Capitol Hill, the CIA set up a secure computer network somewhere in northern Virginia. The agreement, according to Mrs Feinstein, was that after setting up the network the CIA would no longer have access to it.

In May 2010, staff on the committee noticed that some of the documents they had already examined had vanished from the network. Mrs Feinstein says that, when confronted with this, the CIA first denied that the documents had gone and then, deploying the first reflex of office workers everywhere, blamed the IT department. Later on, the agency claimed that the order had come from the White House.

The most sensitive of the vanished documents is an internal CIA review of the rendition, detention and interrogation programme, which is said to be more damning of the agency’s activities than its bosses have been in public.

The CIA thinks that the intelligence committee ought not to have had access to the document, and certainly ought not to have made a redacted copy and locked it away in a safe in the Hart building, a modernist block diagonally opposite the Capitol where some senators have offices. So concerned was the agency that the committee had a copy of the internal review that the CIA’s chief lawyer brought the removal of this document to the attention of the Justice Department.

It was this move that seems to have prompted Mrs Feinstein to speak publicly about an argument that had been kept secret for several years. Her accusations are remarkably direct. In her speech she noted that the same lawyer who had asked the Justice Department to look at what her staff had been doing had been a lawyer in the CIA unit that managed and carried out the rendition, interrogation and detention programme under investigation. Mrs Feinstein added that this lawyer’s name appears more than 1,600 times in her committee’s report. Though it has yet to be declassified, those mentions are unlikely to be flattering.

By chance John Brennan, the CIA’s director, was scheduled to give a rare public speech, at the Council on Foreign Relations, a think-tank, shortly after Mrs Feinstein accused his agency of undermining her investigation. Mr Brennan said that the CIA has had “spirited and even sporty discussions” with its congressional overseers, but that relations between them and the agency were generally good.

He also stuck up for his staff. It was important, he said, to protect the reputations of “the women and men who faithfully did their duty in executing this programme”. As for the accusation at hand, he reckoned that “a lot of people who are claiming that there has been this tremendous sort of spying and monitoring and hacking will be proved wrong.”

Even if he is proved right, by crossing Mrs Feinstein the CIA has lost its most influential ally in Congress. Members of both houses, many of whom have been supportive of the intelligence services since the Snowden leaks, are sensitive about the privileges of their office. Any hint that the CIA is thwarting Congress is likely to unite members who can agree on nothing else. For the president, who has already announced reforms to the NSA that are proving hard to put into practice, changing the workings of the secret state has just become more complicated. When pondering this he should remember that the CIA’s actions are constrained by law, but also by the memory of its past mistakes. Making public the assessment of a now-defunct programme is part of this.