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.

In 2011, after dismissing hundreds of drug cases in New York after the NYPD mishandled evidence, the Judge said, when sentencing a police officer for planting drugs on a suspect:

I thought I was not naive.... But even this court was shocked, not only by the seeming pervasive scope of misconduct but even more distressingly by the seeming casualness by which such conduct is employed.”

Another big reason drug cops lie is the promise of federal money:

In the war on drugs, federal grant programs like the Edward Byrne Memorial Justice Assistance Grant Program have encouraged state and local law enforcement agencies to boost drug arrests in order to compete for millions of dollars in funding. Agencies receive cash rewards for arresting high numbers of people for drug offenses, no matter how minor the offenses or how weak the evidence.

Another: get tough on crime policies, which encourage police to boost their numbers when it comes to stop and frisk and arrests. As one NYPD cop told a reporter:

“At the end of the night you have to come back with something. You have to write somebody, you have to arrest somebody, even if the crime is not committed, the number’s there. So our choice is to come up with the number.”

Why do they get away with it? Most defendants realize that if a jury is given a choice between believing a cop in his blue uniform or a defendant in a jumpsuit, they are far more likely to believe the cop. They know the jury is thinking, "He must have done something wrong or he wouldn't be sitting there." So they take a deal to lesser charges, even if innocent, to avoid the harsher penalty they would receive if convicted at trial.

This isn't exactly huge news -- in 1982 Alan Dershowitz wrote 13 truths about what he called "The Justice Game" in his book, The Best Defense. Among them:

III. It is easier to convict guilty defendants by violating the constitution than by complying with it, and in some cases it is impossible to convict guilty defendants without violating the constitution.

IV. Almost all police lie about whether they violated the Constitution in order to convict guilty defendants.

V. All Prosecutors, Judges and Defense Attorneys Are Aware of Rule IVI.

VI. Many prosecutors implicitly encourage police to lie about whether they violated the Constitution in order to convict guilty defendants.

VII. All judges are aware of rule VI.

VIII. Most trial judges pretend to believe police officers who they know are lying

IX. All appellate judges are aware of rule VIII, yet many pretend to believe the trial judges who pretend to believe the police officers.

X. Most judges disbelieve defendants about whether their constitutional rights have been violated, even if they are telling the truth.

XI. Most judges and prosecutors would not knowingly convict a defendant who they believe to be innocent of the crime charged (or a closely related crime).

XII. Rule XI does not apply to members of organized crime, drug dealers, career criminals, or potential informants.

XIII. Nobody really wants justice.

But 30+ years later, it seems things have not changed. One step in the right direction would be to end quota systems (including those that supposedly don't exist) in places they are against the law. Another would be to end financial incentives to police, such as by cutting off the federal money that goes to drug task forces.

Until these and other changes are made, and people care enough to demand them, we are destined to continue as America: Prison Nation.