For more than 20 years, FBI headquarters in Washington knew that its agents in Boston were using professional killers and mob leaders as informants and shielding them from prosecution for serious crimes including murder, The Associated Press has learned.

Until now, the still-unraveling Boston FBI scandal has been portrayed largely as the work of a handful of local agents -- mavericks willing to deal with the devil to bring down a Mafia family.

But documents obtained by the AP directly connect FBI headquarters to a pattern of collusion with notorious New England killers.

The AP found 20 field memos from Boston agents to the FBI director's office, along with six replies, showing that headquarters was informed about the abuses and condoned them.

The field memos, written between 1964 and 1987, made it clear to Washington that the informants had killed and were likely to kill again, describing one of them as "the most dangerous individual known" in the Boston area. The memos also alerted the director's office that two of the informants were crime bosses, active "at the policy-making level" of criminal enterprises in Boston.

Headquarters also knew that the informants were being shielded from other police agencies by its agents in Boston. It knew, for example, that one informant who masterminded a murder was allowed to go free as four innocent men were sent to prison in his place.

Sometimes, it appears, headquarters was directly involved in protecting the informants. In 1983, for example, Boston agents shielded two of them from questions about the murder of a jai alai operator. Senior FBI officials in Washington gave the order to snuff out the investigation, the deputy chief of the FBI's Boston office at the time told the AP in a recent interview.

J. Edgar Hoover, William Sessions and William Webster headed the FBI in the years when the field memos about the informants were written. Whether they saw them is unknown.

Cartha DeLoach, an assistant FBI director under Hoover, says his late boss did not always read field memos, adding that he can't remember seeing the Boston memos himself. Webster and Sessions declined to be interviewed.

It is uncertain who at FBI headquarters read the memos, but someone was paying attention. In six responses, all but one unsigned, the director's office welcomed the informants and praised their FBI field handlers.

A spokesman for the FBI in Washington declined to comment for this story, citing ongoing investigations and lawsuits.

The AP found the FBI memos in the files of a congressional committee that has begun investigating the abuses, and in records of related court proceedings.

More than $1 billion in lawsuits have been brought against the government by victims of crimes committed by the informants while they were under FBI protection.

The roots of the scandal lie in the 1960s, when the FBI -- which had been devoting many of its resources to investigating Communists -- came under pressure to crack down on the growing power of organized crime.

"They were starting to get heat from the country and the media that not enough was being done about the Mafia," said U.S. Rep. Dan Burton, chairman of the committee investigating the informant abuses. "I think J. Edgar Hoover was sensitive to that."

In Boston, FBI agents responded by recruiting two hit men as informants and by forging an alliance with the Winter Hill Gang -- vicious thugs eager to seize control of the rackets from the Patriarca Mafia family.

The nature of the arrangement, as disclosed in recent criminal proceedings: In return for information about the Mafia, Boston agents looked the other way as the Winter Hill Gang sold drugs, stole and murdered, even tipping them off when the state police and federal drug agents were on their trail.

Both sides got what they wanted. The Patriarca crime family was devastated by federal prosecutions, and the Winter Hill Gang took over Boston-area rackets.

Lawyers representing victims of violence by FBI informers long suspected that Washington played a role in the affair, noting that high-level informants required approval from FBI headquarters. "Either they knew, or they didn't want to know," said lawyer Edward Hinchey.

But until the 26 field memos and replies surfaced, there was little evidence. The memos -- a couple of which have previously been reported by New England newspapers -- somehow survived what one Justice Department lawyer called the routine destruction of many FBI documents involving the informants.

The arrangement between the Boston agents and the gangsters remained secret until 1995, when Massachusetts state police and federal drug agents finally built a racketeering case against the Winter Hill Gang. Its leader, James J. "Whitey" Bulger, and his top lieutenant, Stephen J. "The Rifleman" Flemmi, were indicted along with five others.

Tipped off by a Boston FBI agent, Bulger escaped and remains at large. The others were arrested.

Flemmi promptly protested that he and Bulger were FBI informants and that their crimes had been committed under the protection of the agency. Mark L. Wolf, a U.S District Court judge in Boston, held hearings on Flemmi's claim, and the story began to tumble out.

Wolf concluded that more than a dozen FBI agents had violated the law or bureau regulations. So far, one, John Connolly, has been convicted of racketeering and obstruction of justice and is awaiting sentencing; and another has been granted immunity for testimony. Both had also accepted bribes from informants they were protecting.

The Hit Men

Boston FBI agents trying to recruit Vincent J. "The Bear" Flemmi as an informant knew what he was from the start -- and made sure the FBI director's office knew, too.

Stephen Flemmi's younger brother spoke openly of his "plans to become recognized as the No. 1 'hit man' in this area," Boston agents told Washington in a June 4, 1964, memo.

At least four field memos informed headquarters that Vincent Flemmi planned to kill a small-time hoodlum named Edward "Teddy" Deegan in a dispute over money.

A March 10, 1965, memo, for example, said Vincent Flemmi had asked Mafia bosses for permission to kill Deegan. And hours before the murder, Boston agents reported that mob enforcer Joseph "The Animal" Barboza, had joined the plot.

Deegan's body turned up in a Chelsea, Mass., alley on March 12, 1965. A week later, a memo to headquarters named six men, including Vincent Flemmi and Barboza, as the killers, describing the murder in detail, right down to who fired the first shot.

An unsigned response from FBI headquarters directed Boston agents to tell Chelsea police what they knew. But soon, the FBI had another idea. The agency, it seemed, didn't want Vincent Flemmi in prison. It wanted him on the streets, as an informer.

On June 4, 1965, FBI records show, the director's office demanded a progress report. Was he ready to inform?

Yes, Boston replied, adding that Vincent Flemmi was suspected in eight murders and that "from all indications, he is going to continue to commit murder."

Soon, FBI memos show, Boston agents also recruited Barboza, convincing him that his Mafia employers had turned on him.

Boston told the director's office in a June 20, 1967 memo, that Barboza was the most dangerous man in the region, "a professional assassin responsible for numerous homicides." He was also unreliable, Boston reported -- a man willing to encourage perjury to spare himself a long prison term. He had also vowed never to incriminate his friend, Vincent Flemmi.

But with the promise of a light sentence for his role in the Deegan murder, Barboza soon became a star witness in three Mafia trials.

A Massachusetts jury trusted his word and convicted six men in the Deegan case. Vincent Flemmi and two others identified as the killers in memos Boston agents had sent to headquarters were never charged.

Instead, FBI files show, the bureau stood by as Barboza's false testimony convicted four men who had no connection to the crime. Two died in prison, and two others were released in recent years, exonerated only after the scandal broke.

Barboza had implicated two of them to settle street grudges. The others, though blameless in Deegan's murder, were known Mafia figures.

Barboza would later tell his lawyer, F. Lee Bailey, that he had to offer up big names to seal his plea deal with the FBI.

After the convictions, a July 31, 1968, field memo requested letters of commendation for Barboza's handlers. Hoover sent a personal reply:

"The successful prosecution of these subjects was a direct result of your noteworthy development of pertinent witnesses."

In return for his testimony, Barboza was released after serving five months for the Deegan murder and relocated with a new identity.

Before long, however, he was threatening to recant his testimony unless given $9,000 for plastic surgery to change his appearance.

If Barboza -- who had changed his name to Baron -- were to recant, mob convictions "might be overturned and plunge the government into protracted and acrimonious litigation," two Justice Department lawyers who worked closely with Boston FBI agents warned their Washington supervisor in a Feb. 12, 1970 memo.

"We recommend that by some manner or means, Baron's request be honored to the degree possible," said the memo from Edward F. Harrington and Walter T. Barnes.

Six months later, Barboza recanted his testimony; but soon he changed his mind again, standing by his original story.

Barnes, now retired, said that, as best he can recall, some money was approved for Barboza. At the time, he had no reason to believe Barboza had lied on the witness stand, Barnes added in a recent interview. Harrington, now a federal judge in Massachusetts, declined comment.

In 1976, the Patriarca family found Barboza and exacted its revenge, shotgunning him on a San Francisco street.

Vincent Flemmi died in prison in 1979 after Massachusetts authorities convicted him of attempted murder in another case.

"The Bosses"

Bulger and Vincent Flemmi's brother, Stephen, were just starting their rise in the underworld when Boston agents recruited them as informants. The agents told headquarters what kind of men they were.

For example, a 1964 field memo described Stephen Flemmi's plot to "whack" somebody.

On Feb. 8, 1967, Boston informed headquarters that Stephen Flemmi was being upgraded to a "top echelon" informant -- even though he was "suspect of possibly being involved in gangland slayings."

By 1981, the bureau had adopted rules prohibiting such arrangements. "Informants shall not participate in acts of violence" and "shall not initiate a plan to commit criminal acts," the rules said.

Yet in 1983, when Bulger was upgraded to "top echelon" informant, a field memo said he was "the titular head of the Winter Hill mob and as such sits as an equal at the policy-making level" with New England Mafia leaders.

Boston kept headquarters apprised of Stephen Flemmi's rise, too, alerting them, in a Nov. 25, 1987, memo that he was also a "policy-making" member of the Winter Hill Gang.

The director's office responded with a message of congratulations for the way the informant was being handled.

Throughout the 1980s, local and state police tried to build a case against Stephen Flemmi and Bulger, but the pair was always one step ahead of them. The reason: they were being tipped off by Boston agents, testimony in recent criminal cases has revealed.

FBI headquarters also may have lent a hand.

In 1983, for example, FBI agents in Oklahoma suspected the pair in the murder of Roger Wheeler, the head of World Jai Alai, who was shot between the eyes in Tulsa after discovering that someone was skimming money from his business.

When Oklahoma agents sought to interrogate Bulger and Stephen Flemmi, Robert Fitzpatrick, then deputy chief of the bureau's Boston office, deflected suspicion from them and blocked the interrogations.

He was instructed to do so during a meeting in Washington with top FBI officials including Sean McWeeney, head of the FBI's organized crime section under Webster, Fitzpatrick told the AP in a recent interview.

"It was to protect Whitey Bulger," said Fitzpatrick, now retired. "That was part of the discussion."

McWeeney, also retired, did not reply to requests for an interview.

In the end, however, even the FBI could not protect the informers forever.

Today, Stephen Flemmi is serving 10 years for obstruction of justice and other offenses and awaiting trial on federal racketeering charges that link him to 10 murders.

Bulger, still on the run, is also under indictment for racketeering. Federal prosecutors blame him and his gang for 21 killings.

Eleven of them occurred while he was an FBI informant.