Police and prosecutors rely heavily on informants in drug cases, because the vast majority of drug arrests in the United States are for simple possession -- often marking the first time a person encounters the criminal justice system. This also means there's almost always at least one person higher in the drug distribution chain.

It is common for law enforcement to put pressure on drug defendants to name dealers, distributors or "kingpins" in exchange for immunity or an easier sentence. Because mandatory minimum sentences often apply to drug crimes, this dealmaking is extremely common in drug cases.

Americans who use drugs have much to fear from informants. Because asset forfeiture laws allow police to seize money and property from anyone merely accused of drug activity, a simple phone call from an informant can separate a law-abiding citizen from everything he or she owns. In the case of a mistaken identity or an informant simply lying to get out of trouble, it is extremely difficult for a property owner to reclaim seized property.

Police may pressure drug informants to continue informing once they've already made a successful case. Informants often need police protection because of the risk of retaliation by those they've turned in or their associates. By the same token, police can curry favor with their superiors by arresting and jailing more people on drug charges. Jim Redden's book "Snitch Culture" gives examples of this business relationship, including a case of a professional informant who made tens of thousands of dollars selling drugs while working for police. He was allowed to keep the money and the drugs.

This police protection doesn't always work. One example is an $80 crack bust that killed a Washington, DC resident. A drug user, Eric Butera, agreed to buy crack using marked bills to create an excuse for police to raid a reputed crack house in 1997. He was turned away, robbed and beaten. Police didn't find his body for 40 minutes. During the subsequent wrongful-death suit, a former police official testified that officers failed to follow protocol during the sting and parked too far away to protect Butera. A jury awarded Butera's family nearly $100 million in damages in 1999, though the verdict was later reduced to little more than $1 million.

More information:

• Justice Policy Institute
• The Sentencing Project
• Snitch: How Informants Have Become a Key Part of Prosecutorial Strategy in the Drug War