WASHINGTON, D.C. (CNN)-

Chief Tom Jackson has said the claim that officers are more likely to stop blacks is more perception than reality.

Other cases, though, went well beyond that.

The family of Jason Moore recently filed a lawsuit accusing police of excessive force, claiming he died of cardiac arrest September 17, 2011, after police fired Tasers at him.

The family says that Moore, who they say suffered a psychological disorder, was walking around naked and posed no threat to police.

It’s not clear which cases, specifically, the new federal investigation will examine. The probe will not focus on law enforcement’s response to Brown-related protests, since that effort involved numerous agencies and Ferguson did not lead this multi-agency effort.

Ferguson will be the latest of many local police and sheriff departments nationwide to be subject to such a federal investigation, which Toobin explains are launched “when there are persistent allegations of misconduct.”

This April, for instance, the Justice Department lambasted police in Albuquerque, New Mexico, for what it characterized as a longstanding history of police brutality and unnecessary deadly force, sometimes “in an unconstitutional manner.” The report laid out several measures to address the problems, such as changing policies, training procedures and recruitment protocol.

Police departments in Los Angeles, Pittsburgh, Cincinnati and elsewhere have agreed to Justice Department plans to address controversial policies and patterns of alleged misconduct.

But nowhere has the federal agency come down harder than on the New Orleans police department, which has been plagued for years by allegations of corruption, excessive use of force, illegal searches and widespread racial discrimination.

In July 2012, Attorney General Eric Holder detailed a consent decree — which he called the most wide-ranging such agreement in U.S. history — that includes more than 100 recommendations dealing with virtually every aspect of the department.