Mr. Booker, who has staked his political future on making the city safer, ticked off a list of new initiatives that he credits with reducing crime: a fugitive apprehension project, a unified narcotics squad, a hot line for tips, more police officers on the street and the renewed embrace of New York City’s Compstat system.
The police director, Garry F. McCarthy, has pointed to other factors as well, saying the drop in homicides could be tied to a sharp increase in arrests, including the arrests in January of several gang members, a result of the department’s new collaboration with federal law enforcement agencies.
“We are seeing the result of all that work, and all that activity,” Mr. Booker said. “The trend line is heading in the right direction.”
At the news conference, Mr. McCarthy reported that a Columbia University professor had placed the odds of Newark going 43 days without a murder at one in 111,482.
“There’s no statistical anomaly here,” Mr. McCarthy said. “Ten days can be a statistical anomaly. But the fact of the matter is, there’s a science to policing.”
But even among the scientists, or criminologists, there are major disagreements about the ways in which police practices affect the crime rate. Andrew Karmen, a sociologist at John Jay College of Criminal Justice, talked about one of the prevailing splits.
“How much of the reduction can be credited to the police and to the criminal justice process?” he asked. “How much is due to underlying social conditions?”