"Officers themselves were telling me about how the news over the last 15 months have impacted their instincts -- do they stop, or do they keep driving? When I stop here, is it going to be my career on the line?" Emanuel said this week, CNN affiliate WBBM reported.
His voice is the latest in a growing chorus of officials throughout the country who claim law enforcement officers are under siege.
Distrust of police, in the wake of controversial deaths by officers in Ferguson, Missouri and elsewhere, has resulted in a torrent of anti-police rhetoric and a string of deadly attacks against officers, they say. Those factors have also fueled crime in many American cities.
"It is having an impact on the safety we want to see throughout the city of Chicago," Emanuel said.
In 2012, Chicago was described as the "murder capital" of the United States after the city registered more homicides than any other city, with 503.
Last month, the FBI's 2014 statistics showed Chicago had 411 killings -- more than New York's 333 murders and Los Angeles' 260 murders. Chicago has a smaller population than both those cities. In fact, the FBI figures showed that Chicago's murder count barely changed from the prior year.
The city's continuing violence shows that 2015 could see even more homicides than last year, according to a recent tally by the Chicago Tribune.
"We have allowed our police department to get fetal and it is having a direct consequence," Emanuel said last week at a meeting of the nation's top law enforcement officers and elected officials, The Washington Post reported.
"They have pulled back from the ability to interdict ... they don't want to be a news story themselves, they don't want their career ended early, and it's having an impact."
But the president of Chicago's police union, Dean Angelo, said officers are not holding back.
"I don't think they're standing down," he told WBBM. "I don't think they're not engaging in police work because they're on tape."
Still, some officials claim officers are not only standing down but also becoming targets.
When Deputy Darren H. Goforth, a 47-year-old father of two, was gunned down in late August near Houston, Harris County District Attorney Devon Anderson said the slaying signaled open warfare on law enforcement.
And a Birmingham, Alabama, police detective pistol-whipped unconscious that same month said he hesitated to use force because he didn't want to be accused of needlessly killing an unarmed man.
"It's almost a radical rhetoric causing officers to say, 'Wait a second, I'm out here to serve the public. I saved a little old lady from a purse snatching. I gave CPR on the highway and saved somebody. Now, I'm a villain?'" Chuck Canterbury, president of the national Fraternal Order of Police, a union representing more than 300,000 officers, told CNN last month.
The raw numbers -- at least, in terms of officers dying by firearms -- do not show them becoming targets.
Nationally, police deaths are down 21% this year, compared with the same period last year, according to the National Law Enforcement Officers Memorial Fund. There have been 30 firearms-related deaths this year, including two in training accidents, and 38 in 2014. Traffic accidents -- followed by shootings -- are the leading cause of police deaths.
"Do police officers feel under siege? Yes, they do feel that way. I've heard a lot of them say that," said David Harris, a University of Pittsburgh School of Law professor and an expert on policing.
"But there's no evidence of the so-called Ferguson effect -- that police are hesitating to do their jobs -- or that criminals are being emboldened by the rhetoric. They're not doing their jobs any differently. The job is harder in the last year, but they aren't just lying down."
Darren Goforth was pumping gas into his patrol car August 28 when a man identified as Shannon J. Miles approached from behind and shot him 15 times, officials said. In 2012, Miles was found mentally incompetent to stand trial in another case.
Goforth's uniform made him a target, and a "dangerous national rhetoric" is partly to blame, said the deputy's boss, Harris County Sheriff Ron Hickman.
"This rhetoric has gotten out of control," Hickman said the morning after the shooting. "We've heard 'black lives matter,' 'All lives matter.' Well, cops' lives matter, too. So why don't we just drop the qualifier, and just say 'Lives matter,' and take that to the bank?"
"Black Lives Matter" became a rallying cry of protesters around the country last year after a white police officer in Ferguson killed unarmed black teen Michael Brown, and a black man named Eric Garner died from an apparent chokehold by a white New York police officer.
"It is a very tough time to be a police officer at this moment," said Cedric Alexander, the DeKalb County, Georgia, police chief and former national president of the National Organization of Black Law Enforcement Executives.
This year, three slain officers were targeted because they were law enforcement, according to Canterbury. The attacks came at a time of unprecedented hostility toward the police, he said. In 2014, nine officers were ambushed and killed, he said.
"A lot of officers are being too cautious because of what's going on in the media," said the officer, who asked to remain anonymous over concerns for the safety of his family. "I hesitated because I didn't want to be in the media."
Morale among rank-and-file members is low, Canterbury said.
"Agencies all over the country are losing officers at a rapid pace," he said. "They're unable to hire. They are in some cases reducing standards so that they can try to fill jobs because they need bodies. I don't know of a department in the country that is not having a problem recruiting."
In Hawthorne, California, Sgt. Chris Cognac last month said police officers have to reestablish trust with the communities they serve.
"People are intimidated by the police," he said. "They're intimidated by the uniform, intimidated by the equipment we carry. ... A lot of times we don't really have the chance to talk to people."