The tip comes from a confidential informer: Someone has a gun. Ten or more minutes later, police officers find a man matching the informer's detailed description at the reported location. A gun is discovered; an arrest is made.

That narrative describes how Jeffrey Herring was arrested last year by police officers in the 67th Precinct in East Flatbush, Brooklyn. It also describes the arrests of at least two other men, Eugene Moore and John Hooper, by some of the same officers.

The suspects said the guns were planted by the police....