"Traditional police corruption usually involved a mutually beneficial arrangement between criminals and police officers (e.g., the former offered the latter bribes in exchange for immunity from arrest). In contrast, several studies and investigations of drug-related police corruption found on-duty police officers engaged in serious criminal activities, such as (1) conducting unconstitutional searches and seizures; (2) stealing money and/or drugs from drug dealers; (3) selling stolen drugs; (4) protecting drug operations; (5) providing false testimony; and (6) submitting false crime reports."

Source

General Accounting Office, Report to the Honorable Charles B. Rangel, House of Representatives, "Law Enforcement: Information on Drug-Related Police Corruption (Washington, DC: USGPO, May 1998), p. 8.
http://www.gao.gov/products/G…