Police officers may accept bribes or other favours offered by those who would otherwise face prosecution. They may be intimidated by organized crime and in turn may use intimidation against people who oppose the interests of their benefactors or who threaten to expose their complicity. Corruption can be large-scale where the illegal interest protected by police corruption is considerable and where the benefits of complicity are highly rewarding.
Early in 1985, Mexico began investigating claims that many of its top police officials were being bribed for their participation in crime cover-ups, particularly in relation to the illegal drug trade. Several were fired and arrested. In 1993 it citizens were reportedly still used to the mordida, namely the routine demand for a bribe by a patrolman after an offence, which may have been invented for the occasion. Patrolmen claimed that they themselves faced extortionate demands for bribes from their superiors. Cases of police committing extortion, rape and even murder were not unusual. There was much evidence of police involvement in the drug trade. Many were accused of being criminals by members of the Mexico City assembly. In 1985, 37 police generals were dismissed in Peru. In 1994 almost all the senior police officers of Rio de Janeiro were suspended after their names were found on the alleged payroll of the city's illegal lottery controlled by organized crime.
In a five year period in the mid-1980's 170,000 Soviet police officers were fired for offenses from misconduct to murder. Between 1979 and 1987 some 27 police officers in the state of Queensland, Australia received about $2.5 million in bribes. In the Philippines most of the big political murders, including that of opposition leader Aquino in 1983, remain unsolved, because the army is reluctant to use its authority to investigate military abuses in the Marcos era. In 1993 the police chief of Rome was forced to resign after admitting knowledge of illegal funds kept by a civilian secret service agency to payoff politicians.
In New York in 1993 the Mollen Commission appointed by the mayor heard a large amount of evidence that the city's police department contained numerous corrupt officers involved in: selling drugs, taking bribes, stealing money and drugs from drug dealers, brutalizing innocent bystanders, commandeering the services of prostitutes, and breaking many laws. One officer managed a major cocaine operation out of his house. The New York police department has been the subject of occasional major scandals throughout its existence (in the 1890s, positions in the police department were bought at amounts up to US$15,000 depending on what the position could generate). The 1993 investigation followed the Knapp Commission in 1971 at which evidence was presented concerning a pattern of extortion rings and payoffs, and officially sanctioned corruption. This system made it extremely difficult to get police superiors to investigate police graft even when hard evidence was offered. Penalties for reporting on colleagues were severe. On both occasions evidence was presented that potentially exemplary officers were constantly exposed to arguments that they should ignore the law and keep silent about it. Beyond simply accommodating criminals, police were effectively becoming criminals themselves. Civilian complainants were harassed and their evidence was ignored.
Corruption was first reported in 1969 in the London police force with discovery of a group effectively providing any form of service to criminals, including bail. Another corrupt unit was identified in 1972; the subsequent investigations led to the resignation of 478 officers, many in anticipation of criminal proceedings. Some high profile trials involved senior officials receiving payments to protect criminals from prosecution. The Operation Jackpot was launched in 1991 to investigate the most serious allegations of police corruption in the UK in 20 years, including drug dealing, conspiracy to pervert the course of justice, theft, assault and criminal damage. In 1993 another inquiry was launched into allegations of corruption involving detectives said to have sold sensitive information to drug dealers, but only after media exposure. It was acknowledged that the police had no way of effectively monitoring their own activities. In 1992 a series of miscarriages of justice caused by police fabrication of evidence or perjuring themselves had revealed a culture of institutional corruption with some 800 possible cases requiring further investigation. Inquiries initially centred on the West Midlands Serious Crimes Squad for which 23 cases brought between 1981 and 1991 were shown to be without foundation; as a consequence more than 50 detectives had to be transferred into non-operational positions. Although the Police Complaints Authority recommended that up to 16 officers should be prosecuted the Director of Public Prosecutions disagreed, supposedly because of insufficient evidence.