Kevin Johnson

USA TODAY

WASHINGTON — FBI Director James Comey once again raised the prospect that sustained spikes in violent crime in many U.S. cities could be linked to a pull back by police who fear the scrutiny of a plethora of cellphone video trained on law enforcement actions across the country.

Citing rising murder numbers in some of America's largest cities, including Chicago and Las Vegas, Comey said the phenomenon of "viral videos'' may be prompting changes in the way officers are policing their cities.

"I was worried about it last fall,'' Comey told reporters at a Wednesday briefing, referring to continuing surges in violence. "And I am, in many ways, more worried now. ...The people dying are almost entirely black and Latino. I don't know what the answer is. But, holy cow, do we have a problem.''

And the director said that "changes in the way police may be acting ... could well be at the heart of this'' troubling trend.

The director’s remarks echoed a similar assessment he provided during separate appearances last fall in Chicago, which put him at odds with some in law enforcement and the White House.

At that time, White House spokesman Josh Earnest and Attorney General Loretta Lynch said that the available data did not support such a conclusion. The White House and Justice Department did not address Comey's remarks Wednesday.

But Comey said he continues to hear from local law enforcement authorities who fear that officers have become less aggressive in carrying out their duties, if only marginally, out of concern that their actions will be captured on video and dissected publicly.

While Comey could not absolutely attribute the crime spikes to less aggressive policing, he urged academics and others to examine the possible relationship.

"It's a problem (violent crime) that most of America can drive around,'' the director said. "From the Las Vegas strip, you can't tell that more 60 people have been murdered in Las Vegas this year. From the Miracle Mile in Chicago, you can't hear the sounds of gun shots that have killed more than 200 people so far this year.

"There is a perception that police are less likely to do the marginal things that suppress crime,'' the director said.

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Comey said he had become newly concerned about the issue after reviewing quarterly crime data collected by the Major Cities Chiefs Association, a law enforcement group representing the nation's largest cities. Many of the more than 40 cities represented in the in the group's review, he said, were reporting problems with violence.

Darrel Stephens, executive director of the chiefs' association, could not be immediately reached for comment.

But Chuck Wexler, director of the law enforcement think tank Police Executive Research Forum, said police officials were scheduled to meet later this month in New York to discuss the possible causes of the scattered surges in violence. That meeting, Wexler said, would address the issue known as de-policing.

"Why is crime going up in some cities and not in others? It is a question that police chiefs are asking,'' Wexler said.