"Mr. Keane, in his Chronicle article, offered two major reasons the police lie so much. First, because they can. Police officers “know that in a swearing match between a drug defendant and a police officer, the judge always rules in favor of the officer.” At worst, the case will be dismissed, but the officer is free to continue business as usual. Second, criminal defendants are typically poor and uneducated, often belong to a racial minority, and often have a criminal record. “Police know that no one cares about these people,” Mr. Keane explained.
"THE pressure to boost arrest numbers is not limited to drug law enforcement. Even where no clear financial incentives exist, the “get tough” movement has warped police culture to such a degree that police chiefs and individual officers feel pressured to meet stop-and-frisk or arrest quotas in order to prove their “productivity.”
"Remarkably, New York City officers have been found to engage in patterns of deceit in cases involving charges as minor as trespass. In September it was reported that the Bronx district attorney’s office was so alarmed by police lying that it decided to stop prosecuting people who were stopped and arrested for trespassing at public housing projects, unless prosecutors first interviewed the arresting officer to ensure the arrest was actually warranted. Jeannette Rucker, the chief of arraignments for the Bronx district attorney, explained in a letter that it had become apparent that the police were arresting people even when there was convincing evidence that they were innocent. To justify the arrests, Ms. Rucker claimed, police officers provided false written statements, and in depositions, the arresting officers gave false testimony.