The [Bronx] court sealed the case file, hiding from view a problem so old and persistent that the criminal justice system sometimes responds with little more than a shrug: false testimony by the police.

[...] "Behind closed doors, we call it testilying," a New York City police officer, Pedro Serrano, said in a recent interview, echoing a word that officers coined at least 25 years ago. "You take the truth and stretch it out a little bit."

[...] An investigation by The New York Times has found that on more than 25 occasions since January 2015, judges or prosecutors determined that a key aspect of a New York City police officer's testimony was probably untrue. The Times identified these cases — many of which are sealed — through interviews with lawyers, police officers and current and former judges.

In these cases, officers have lied about the whereabouts of guns, putting them in suspects' hands or waistbands when they were actually hidden out of sight. They have barged into apartments and conducted searches, only to testify otherwise later. Under oath, they have given firsthand accounts of crimes or arrests that they did not in fact witness. They have falsely claimed to have watched drug deals happen, only to later recant or be shown to have lied.

[...] Many police officials and experts express optimism that the prevalence of cameras will reduce police lying. As officers begin to accept that digital evidence of an encounter will emerge, lying will be perceived as too risky — or so the thinking goes. [...]

Yet interviews with officers suggest the prevalence of cameras alone won't end police lying. That's because even with cameras present, some officers still figure — with good reason — that a lie is unlikely to be exposed. Because plea deals are a typical outcome [...]

"There's no fear of being caught," said one Brooklyn officer who has been on the force for roughly a decade. "You're not going to go to trial and nobody is going to be cross-examined."

[...] Police lying raises the likelihood that the innocent end up in jail — and that as juries and judges come to regard the police as less credible, or as cases are dismissed when the lies are discovered, the guilty will go free. Police falsehoods also impede judges' efforts to enforce constitutional limits on police searches and seizures.