From mid-August through the end of the year in Chicago's West Side Harrison District, there were 15 murders. In the same period last year, there were 25.
Why the drop?
Crime numbers often fluctuate for a variety of reasons, but police believe the key one in this case is an anti-gang strategy that puts a new face on an old idea.
If someone in a gang is arrested for murder, the idea is you put the squeeze on the whole gang.
Not just Chicago police, but the Feds as well want warrants, gun violations, drug trafficking, the works.
That's what police did last summer. After a leader of the Black Souls street gang was charged with murder, 60 other members of his gang were arrested in 60 days for a variety of offenses.
Police focused on some basics: what's the gang structure, who's got rap sheets, who knows who, who's a likely victim and who's most likely to commit a gun crime.
"Unfortunately, in case after case, the offender and victims know each other. In some cases they're related, so it's a unique social network that drives this analysis," Weis said.
Police are using what they call social network analysis. It starts with what street cops know, then that gets analyzed by computer which compares crime patterns and arrests going back in time.
"One thing we know about crime is it's a lot like sex: who you mess around with is going to get you into trouble," said Harvard Professor Andrew Papachristos.
Police say that in part through social network analysis, they've been able to crackdown on a second gang making nearly 200 arrests, many for felonies. They plan yet another "call-in," where leaders of a gang are brought in and given a warning.
"We're gonna bring them in and tell then we're gonna do the same stuff as the first call-in. We told you we're goin' after the most violent street gang in '11 and we did," said Brian Murphy, acting deputy superintendent of the Chicago Police Department.
This is a pilot program currently in use only in Chicago's Harrison Police District.
It is being used with measurable success in other cities, though the gang structure in Chicago is considered more complex and gun crime more frequent.
This is the program that generated some controversy when it began last summer with critics suggesting that the police superintendent was negotiating with gang leaders.
The reality was it was notification, not negotiation, and that criticism has now fallen away.