Loretta Lynch: no data to support 'Ferguson effect' policing theory

US attorney general Loretta Lynch said on Tuesday there was “no data” to support the idea that law enforcement officers are policing less aggressively because of increased scrutiny of their tactics following a series of highly publicized killings mostly of black men.

Lynch spoke during a House judiciary committee hearing on Tuesday and discussed the controversial theory, termed the “Ferguson effect”, in the wake of the fatal police shooting of unarmed black teenager Michael Brown in the Missouri city last year.

“While certainly there may be anecdotal evidence there, as all have noted, there’s no data to support it,” she said during an oversight hearing on the Justice Department held by the committee.

Representative John Conyers of Michigan asked Lynch to address the topic, noting that he knew of “no real evidence to substantiate this claim”.

“Our discussion about civil rights and the appropriate use of force and all police tactics can only serve to make all of us – community members and police officers – safer,” Lynch said.

Lynch is the most recent law enforcement official to enter the debate over whether the “Ferguson effect” phenomenon exists and is responsible for an increase in violent crime in some American cities this year.

FBI director James Comey has cited anecdotes to support the theory, and has been joined by Chicago mayor Rahm Emanuel and Chuck Rosenberg, head of the US Drug Enforcement Agency, in blaming an increased focus on police tactics for making officers less aggressive.

The White House said it did not support the hypothesis following Comey’s comments, and Barack Obama dismissed the use of anecdotal evidence in a speech to top law enforcement officials in Chicago last month.

“We do have to stick with the facts,” the president told the International Association of Chiefs of Police. “What we can’t do is cherry-pick data or use anecdotal evidence to drive policy or to feed political agendas.”

Policing experts say there is no existing evidence to support the notion that violent crime is increasing across the county or that any such increase could be attributed to de-policing. The Police Foundation, a nonprofit research group, is set to begin studying the theory.