Answer:
informants are difficult to control
Step-by-step explanation:
Some police departments rely heavily on informants when they are trying to bust drug dealers, the problem is that informant use is not regulated. Three Supreme Court decisions basically allow police officers to use informants freely (Hoffa v. United States, Lewis v. United States, and Osborn v. United States). What makes things worse is that the FBI has a clear guideline related to confidential informants, but every state government has its own and they are generally much looser.
A common police mistake is trusting excessively former drug dealers or users, which has resulted in ways to get back at former "friends/enemies" and competition. The fight against drugs is very complicated and informants sometimes have too much to gain and nothing to lose. Informants put the lives of police officers and alleged criminals on risk, and until some type of regulation can make them accountable for their deliberately wrongful collaborations, the problem will remain.