At the request of his probation officer, Tyrone C. Brown came to a community auditorium here in June and sat alongside about 30 other mostly young black men with criminal records — men who were being watched closely by the police, just as he was.
He expected to hear an admonition from law enforcement officials to help end violence in the community. But Mr. Brown, 29, got more than he had bargained for. A police captain presented a slide show featuring mug shots of people they were cracking down on. Up popped a picture of Mr. Brown linking him to a criminal group that had been implicated in a homicide.
“I was disturbed,” said Mr. Brown, who acknowledges having been involved in crime but denied that he had ever been involved in a killing.
That discomfort was just the reaction the authorities were after.
Mr. Brown, whose criminal record includes drug and assault charges, is at the center of an experiment taking place in dozens of police departments across the country, one in which the authorities have turned to complex computer algorithms to try to pinpoint the people most likely to be involved in future violent crimes — as either predator or prey. The goal is to do all they can to prevent the crime from happening.