It all started with a careless conversation between two police officers.

Last September, Brooklyn South narcotics officer Sean Johnstone told a fellow officer that he had paid his confidential informants with cocaine illegally seized from a crime scene. What Johnstone didn't realize, or had forgotten, was that his conversation was being recorded.

The ensuing internal police investigation has resulted in an embarrassing spectacle for the New York City Police Department and the Brooklyn South narcotics division, which includes Park Slope, Midwood and Coney Island and made 7,400 arrests in 2007. Four officers, including Johnstone, were arrested for illegally providing drugs or money to their confidential informants, while another dozen were suspended or transferred to other duties. The disclosures forced the Brooklyn District Attorney's Office to dismiss charges or vacate convictions in 183 cases, and a new commanding officer was appointed to run the department's narcotics unit.

The revelations focused attention, if only briefly, on the murky world of police and their informants. While giving informants drugs is clearly illegal, a far more contentious debate involves the use of confidential informants even when proper police procedures are being followed. Civil libertarians and legal scholars argue that the practice leads to false convictions, shoddy police work and an erosion of trust in high-crime, low-income communities. On the other hand, experienced prosecutors and police officers contend that, however distasteful the practice, informants are an invaluable investigative tool and that suggestions for reform would limit the effectiveness of the police while having the unintended effect of driving the officer-informant relationship further underground.

The scandal has given renewed life to legislation introduced last year by Brooklyn State Assemblymember Joseph Lentol, which would require law enforcement agencies to publicly disclose information about the use and effectiveness of confidential informants. The legislation would also limit the ability of prosecutors to drop or reduce certain types of charges in exchange for informant information.

The Brooklyn Scandal

Over the last 30 years, police departments have introduced safeguards in an attempt to protect the integrity of the narcotics enforcement process. With some notable exceptions, the kind of brazen corruption depicted in films such as "American Gangster" and "Serpico" appears to be a thing of the past.

Typically, undercover officers who seize drugs or money are not allowed to register the contraband on their own. Instead, a backup team of officers, with a supervisor, is supposed to lead the vouchering process.

Police departments also have procedures in place for the payment of confidential informants. To High Point, North Carolina Police Chief Jim Fealy, a nationally recognized innovator in narcotics enforcement, the "industry standards" include a careful accounting of the amount expended, along with a requirement that payment is made by no less than two officers. Often a supervisor will randomly accompany the officers to make sure the procedures are being followed and to confirm the informant's identify. At regular intervals, internal affairs officers will audit the books to confirm that all the information adds up.

These procedures appear not to have been followed in Brooklyn. According to reports, two of the four officers arrested on corruption charges in Brooklyn registered 17 bags of cocaine during a drug raid, instead of the 28 bags they had actually recovered, while the other two held back two bags of cocaine and $40. In both instances, the extra drugs and money were used to pay off informants - making it what a law enforcement official called "noble cause corruption."

Many observers expressed their bewilderment at the officers' actions. "Anybody who would do something like that is nuts - completely nuts," one former narcotics undercover officer told the New York Times. "Why would you give the [informant] crack and drugs if you can give them money?"

The most likely explanation is a combination of laziness and lax management. Two of the four arrested police officers worked the night shift, when there tends to be a more relaxed attitude toward procedures. Given the wholesale leadership changes in Brooklyn - four high-level police commissioners, including the head of the department's narcotics division, were transferred - appears that the New York City Police Department is laying a good portion of the blame at the feet of inattentive management.

"What it looks like to me is that these guys took a shortcut and shortcuts will get you in trouble and shortcuts will get you in jail," Raymond Abruzzi, a former high-ranking police officer, told the New York Times.

Fealy praises the department for dealing with the problem internally. "Even in a very good police department, occasionally bad things will happen" he said. "What citizens should look for is a police department that acknowledges [the problem] and deals with it."

A Widespread Practice

Whatever the public thinks of the going-on in Brooklyn, many legal scholars and advocates believe that public outrage should be directed at the mundane, day in and day out grind of recruiting and employing informants, particularly in low-income, high-crime communities hit hardest by the drug trade.

Observers distinguish well-intentioned citizens who provide tips to the police from individuals who co-operate for less noble reasons. In their view, the police get in murky territory when they deal with individuals seeking to settle a score against a former boyfriend or business rival, bargain their way out of an arrest or make a little money. That said, it's almost impossible to prosecute certain types of cases, particularly narcotics cases, without turning to informants who are looking for a break or a buck. "It's not the only way, but it's the easiest way to gain access" to drug markets, said Fealy.

Little is known about the number of informants employed by law enforcement agencies. At the national level, the Federal Bureau of Investigation reports that it employs 15,000 secret informants and the Drug Enforcement Administration about 4,000 at any given time. State and local law enforcement agencies do not report similar information publicly, though most departments, including New York's, keep internal databases that track contacts with informants.

This lack of information has led to widely varying estimates of the total informant population. Loyola Law School Professor Alexandra Natapoff figures that one in 12 black men in poor black communities are active informants at any given time, although she acknowledges that can vary widely from one city to another.

"In some cities, if you believe what the police and prosecutors say, it's not in the culture to use snitches," she said, "while in other places, it's absolutely par for the course."

Experienced law enforcement officials dispute that finding, at least at the local level. For example, Lt. Rudy Tai of the San Diego Police Department, who worked as a supervisor in a narcotics unit, estimates that the average narcotics officer works with between one and three informants.

Generally, federal law enforcement agencies seem much more likely to rely on informants than do local agencies. Under federal sentencing guidelines, cooperating with authorities is the only recognized basis for sentencing leniency, and according to Natapoff, approximately 20 percent of federal offenders -- 30 percent of drug defendants -- received credit for cooperation. And these percentages understate the total volume, because many informants do not receive credit for their information and others have their charges dropped before they reach court.

Local law enforcement agencies are much more cautious about the use of informant information, and many do not allow informants to testify in court. Instead, they are more likely to ask informants to help make a case, such as by introducing an undercover officer to a drug dealer. Experienced officers say that the key is getting independent verification of the information provided.

The Pitfalls of Informants

Critics argue that an excessive reliance on informants leads to lazy police work and has poisoned relationships with residents of low-income, high crime neighborhoods. In the online journal Slate, Alexandra Natapoff wrote that in one view, "criminal snitching is a Frankenstein's monster that has turned on and begun to consume its law enforcement creator."

Natapoff cited one case dropped by prosecutors after the Brooklyn South scandal erupted. An undercover officer had purchased large amounts of cocaine from a dealer, who was later arrested. However, the undercover team working on the case failed to get the drug sale on videotape. When the prosecutor realized that one of the officers involved in the corruption scandal was on the team, she was forced to drop the case.

"The ease of using informants has undermined other traditional law enforcement techniques like undercover work and surveillance," said Natapoff.

Law enforcement officials bristle at that characterization. "I don't see [using informants] as lazy policing," said Fealy. "What are we supposed to do, ignore the information they give us?"

Establishing the bona fides of a confidential informant can be painstaking, requiring a background check and a "test run" purchase of drugs or guns. "A lot of detectives would rather not be involved with informants because it takes a lot of hard work," said Tai. "It's a challenge to recruit good ones."

Many police officers and prosecutors, however, express qualms about aspects of the relationship with confidential informants. They realize that even the small amounts of cash they give informants are often used to buy drugs. Another troubling dynamic is that the police may overlook crimes committed by informants. "Informants may well produce more criminal activity on any given day than they prevent," wrote Natapoff.

The swirl of charges and counter-charges about the use of confidential informants may obscure a counter-intuitive reality about policing in urban communities. Despite skyrocketing incarceration rates, particularly of young African-American men, the problem confronted by most citizens in high-crime areas is police under-enforcement of the law, not over-enforcement. That dynamic was particularly evident in sociologist Sudhir Venkatesh's recent book Gang Leader for a Day: Despite spending nearly a decade hanging out with a drug gang in a Chicago housing project, Venkatesh rarely encountered the police.

To Natapoff, police use of confidential informants contributes to the under-enforcement problem, because the police regularly tolerate the criminal behavior of informants. One could, of course, also reach the opposite conclusion: Abandoning or curtailing the use of confidential informants could make the police even less effective in communities that need them the most.

Bringing the Practice to Light

Deciding which view is correct is difficult because so much about informants is, of necessity, hidden from public view. "It's all hidden," said Ellen Yaroshefsky of the Benjamin Cardozo Law School. "Confidential informants are like the black hole of the criminal justice system."

Lentol's proposed legislation would require law enforcement agencies to publicly disclose information about confidential informants, including the number employed, whether the tips provided led to a conviction or arrest and instances in which prosecutors offered to reduce or drop charges in exchange for cooperation. Individual informants would not be named. In theory, the "sunshine" provisions would give the public the chance to test the claims made by supporters and critics of the practice.

Still, it can be an uphill battle to convince the police of the value of openness and accountability. "I've had well-meaning police officers tell me, 'you're never going to get the police to report their snitches'" Natapoff said. "It's a reasonable concern. We have to give them room to do their job."