As McCarthy and the department's top brass came to City Hall to talk budget, the pressure was on for the city's top cop to explain a murder rate that has gone up 22 percent compared to last year.
Many aldermen and the Fraternal Order of Police are pushing for more cops.
"Every single ward needs police officers and you see certain areas of the city where crime is increasing at a startling rate and the alderman are responding to that," said Fraternal Order of Police's Mike Shields.
But Supt, McCarthy says deployment is just as, if not more, important than numbers when it comes to keeping Chicago safe.
"There is not a 1-1 ratio where this many cops gives us this much crime reduction. It's what those officers are doing when they are on the street," he said.
McCarthy says a new gang violence reduction strategy that includes a gang audit will help figure out where officer are needed.
"What gangs operate in this neighborhood, what turfs do they call their own, what are the membership roles of each of those gangs and who is in conflict with who," he said.
In the mayor's proposed budget, the number of officers will go up a bit, but not enough. For many aldermen, with a budget that does not include fees or tax increases, paying for more cops is an issue.
"The mayor wanted a longer school day, he found the money, the mayor wanted additional after-school programs he found the money. We need more cops on the street, that's clear" said Alderman Ricardo Munoz.
Tracy Siska with the Chicago Justice project is not so convinced more officers are necessary. He is calling for more transparency when it comes to how staffing levels are determined.
"The police department has an analysis done that will show us how many officers we need, how many each district needs, we're just calling for that to be made public," Siska said.
Supt. McCarthy would only say the department is down by 263 officers.
The magic number that is in the budget is 12,500 officers. Many aldermen would like to know how the department came up with that number.
McCarthy said there is no document to explain it.