WHAT INCENTIVES DO LAW ENFORCEMENT OFFICERS HAVE TO COMMIT PERJURY IN CRIMINAL CASES

Your favorite Clearwater Criminal Lawyer has watched with bated breath in numerous criminal trials as hundreds of officers have lined up one by one to testify against my doomed clients. Upon taking the witness stand having sworn to tell the truth they've done everything possible to convince those once fair and impartial jurors to convict. Were those officers always telling the truth?

Manet, Considering Perjury, 1875

It's not uncommon to know that an officer is committing perjury especially when other evidence directly establishes that the officer is simply lying. 
Should the Jury, well and truly try and true, believe that libelous video that seems to show the officer beating all hell out of my client or the trustworthy officer's testimony? And yet the prosecutor will always ask the jury this, "Why would a law enforcement officer ever risk his career to lie under oath about a criminal case?" 
A recent editorial by Michelle Alexander in the New York Times addresses the issue of why officers lie under oath giving some good reasons as to why it happens more often than we think. The article quotes the San Francisco Police Commissioner as follow:

“Police officer perjury in court to justify illegal dope searches is commonplace. One of the dirty little not-so-secret secrets of the criminal justice system is undercover narcotics officers intentionally lying under oath. It is a perversion of the American justice system that strikes directly at the rule of law. Yet it is the routine way of doing business in courtrooms everywhere in America.”

The article mentions the unrelenting pressure to make ever greater numbers of arrests as a significant cause of police perjury. In many police departments the quality of an officer's work is judged based on the number of arrests he makes. 
Here in Tampa Bay the Largo Police Department and the Florida Highway Patrol have the reputation of going to extraordinary lengths to persuade their officers that the only path to advancement is with high arrest numbers causing some officers to speak up about the unrealistic pressure of the quota systems, even as the police agencies deny there is a quota system.
A second cause could be called the War on Drugs Syndrome. This seems to be what has long afflicted the Pinellas County Sheriff's Office in Tampa Bay, Florida who broke the law during investigations of significant drug cases, such as manufacturing marijuana.
The internal thinking of officers must be something along the lines of, "It's a war after all. It's us versus them. They're violating the law. We're the good guys." And the next thing you know Deputies are acting like criminals themselves lying under oath, lying to gain entry into a home or even destroying evidence.