An organized-crime trial in Boston and several other high-profile cases around the country raise questions about whether the United States justice system is being corrupted from within through overzealous reliance on criminal informants.
The issue in Boston arose after it was disclosed that several gangsters - including James "Whitey" Bulger - doubled as government informants.
But more serious is the probability that prosecutors and agents misled judges by withholding information about Mr. Bulger and other informants to maintain the cover of the cooperating criminals. In addition, some suspect the FBI tipped off Bulger to investigations by other agencies so he could continue to provide inside information on the Mob.
If the allegations are true, they suggest prosecutors and agents had a higher allegiance to criminal informants than to the courts.
The danger of relying on criminal informants was shown last week when a California judge ordered the release from prison of Elmer "Geronimo" Pratt, a former Black Panther leader, who served 27 years of a life sentence on a murder conviction.
The judge found that prosecutors at Mr. Pratt's trial deliberately withheld information from the jury that the state's star witness was a convicted felon and FBI informant.
Federal prosecutors investigating Manuel Antonio Noriega for alleged racketeering and drug trafficking failed to disclose to either defense attorneys or the trial judge that the Panamanian general's chief defense lawyer at the time of General Noriega's surrender in 1989 was secretly an informant for the US government.
In the case of New York Mob boss John Gotti, prosecutors won a five-year prison term for Mob underboss and hit man Salvatore "Sammy The Bull" Gravano after he turned against Mr. Gotti. Mr. Gravano had admitted involvement in 19 murders, but prosecutors said his testimony was necessary to convict Gotti.
"It is out of control," says GiGi Gordon, a defense attorney in Los Angles and longtime critic of the widespread use of informants. "All they have done is dirty themselves and dirty up the system by engaging in this tactic," she says.
The reliance on criminal informants means that increasingly prosecutors are asking juries to accept as truth the testimony of murderers and other criminals who have made careers out of lying, cheating, and stealing.
Some critics say government officials appear more than willing to engage in similar conduct.
"We are seeing evidence throughout the country of prosecutors and agents arrested for lying to the courts, for stealing money, for falsifying records," says Hugo Rodriguez, an assistant federal public defender in Miami and a former FBI agent. "We have prosecutors who condone that kind of activity. It is not the exception anymore."
Law enforcement officials say they have to rely on informants to make difficult cases. They say sometimes it takes a criminal to catch a criminal, particularly in cases involving organized crime and ruthless drug traffickers.
But criminal defense attorneys say the technique is overused - that reliance on informants creates the danger that convictions are being purchased by paying an informant enough money or promising a lighter prison term.
"With the kind of money they pass out, some of these people would testify against their own mothers," says Karnig Boyajian, a Boston defense lawyer.
Ms. Gordon adds, "The nature of a criminal is that they will do whatever he or she must do to avoid incarceration - that includes lying, cheating, and stealing, and it can include informing."
At stake in the Boston case is whether the government will be allowed to introduce certain evidence gathered from court-authorized wiretaps in the trial of accused New England Mob leader Frank "Cadillac Frank" Salemme.
To gain authorizations, prosecutors had to show to a federal judge that all other "normal" investigative techniques - including recruiting informants - had been tried and failed. At the time, prosecutors did not disclose the existence of any informants.
The issue is expected to trigger appeals by convicted gangsters who will argue they did not receive fair trials because of government deception.