FBI director James Comey conceded on Monday that he had little evidence to support his theory that a recent increase in crime was caused by heightened scrutiny of the police, as the White House appeared to distance itself from his remarks.

Addressing police chiefs at a conference in Chicago, Comey said he could not be certain that the so-called “Ferguson effect”, following unrest in the Missouri city after the fatal police shooting of an unarmed black 18-year-old last year, had led to a retreat by officers, but said this was “common sense”.

“The question is, are these kinds of things changing police behavior around the country?” said Comey. “The honest answer is I don’t know for sure whether that’s the case … but I do have a strong sense.”



Barack Obama’s press secretary, however, said at a White House briefing on Monday that available evidence “does not support the notion that law enforcement officers around the country are shying away from fulfilling their responsibilities”.

Law enforcement leaders were “on the contrary” reporting that officers were “dedicated public servants, who on a daily basis are putting their lives on the line to serve and protect the communities that they’re assigned to”, said Josh Earnest.

Earnest declined to explicitly say he was disagreeing with Comey’s comments and simply reiterated that law enforcement leaders across the country have indicated otherwise.

During his speech at the annual convention of the International Association of Chiefs of Police, Comey said the surge in criticism and protests against the police was “the one theory that to my mind and to my common sense, does explain” the increase in crime in some major cities in 2015.



Monday’s remarks were the second time in four days he had publicly backed the much-debated theory. On Friday, he told an audience at the University of Chicago Law School that the “YouTube world” in which bystanders frequently film officers on their cellphones was changing police behavior.



Citing a “wind of viral videos” depicting police officers at work that he said was blowing through law enforcement, Comey argued that public outcry often follows directly. “That wind is surely changing behavior, common sense tells me,” he said.



The FBI director’s remarks prompted sharp criticism among activists and some law enforcement thinkers, who have said there is no solid data to support his theory.



The Sentencing Project, a criminal justice nonprofit, has published research indicating that a rise in homicides in the St Louis area predated the death in Ferguson of Michael Brown and the ensuing protests. Bruce Frederick, a senior researcher at the Vera Institute of Justice, wrote last month at The Marshall Project that there was also no “compelling evidence that there has been a pervasive increase in homicides that is substantively meaningful”.

Acknowledging that some regions were “dealing with a serious uptick” in crime, Earnest said the administration was devoting “serious consideration” to this while also attempting to push an overhaul of the criminal justice system through Congress.

Amid rare bipartisan consensus for lowering mandatory minimum sentences for nonviolent drug offenders and other reforms, Earnest said the disproportionate effect of severe sentences on minorities had an impact not just on crime rates, but on “perceptions of fairness and justice in the United States”.

Comey on Monday acknowledged that he had only anecdotal evidence to support the theory, and reiterated an earlier call, similar to those made by Barack Obama and attorney general Loretta Lynch, for law enforcement to collect and publicize more data.



The FBI director did, however, offer cautious praise for elements of the Black Lives Matter movement for the first time, suggesting their work could allow police officers to understand the viewpoints of people in situations different to their own.

During his speech, Comey discussed both Black Lives Matter and a hashtag that has emerged in response, #PoliceLivesMatter, which is used on social media by supporters of law enforcement, many of whom criticize Black Lives Matter activists for allegedly being anti-police.



Public officials have butted heads over what the movement stands for in the past week, after Obama praised the movement on Thursday for raising legitimate concerns about policing practices in the US. New Jersey governor Chris Christie criticized the president for not supporting police, and claimed that Black Lives Matter activists were “calling for the murdering of police officers”.



Comey said both Black Lives Matter and Police Lives Matter had launched important conversations, and that each group could benefit from observing the case made on social media by the other.



“Law enforcement can actually use hashtag Black Lives Matter, to see the world through the eyes of people who are not in our line of work and see how they might perceive us,” Comey said. “And I believe that those members of the black community can use hashtag ‘police lives matter’ to see the world through law enforcement eyes and see the heart of law enforcement.”

Lynch will speak at the conference on Tuesday on a panel discussion about police-community relations. Obama is also scheduled to address law enforcement leaders as part of his ongoing campaign to reform aspects of the criminal justice system.