The Minneapolis Police Department is finally drawing the highest level of scrutiny — a full-scale investigation by the U.S. Justice Department that will look for patterns of unlawful conduct, excessive force and discriminatory policing.

It is a welcome development in a city where mayors and police chiefs alike have struggled for years to effectively reform the department.

U.S. Attorney General Merrick Garland announced the probe Wednesday — one day after former Minneapolis police officer Derek Chauvin was found guilty of murdering George Floyd by deliberately kneeling on his neck for more than nine minutes.

The verdict alone, Garland rightly said, "does not address potentially systemic policing issues in Minneapolis." For that, he said, "pattern and practice" investigations are needed, to "look beyond individual incidents to assess systemic failures," and whether a department "has a pattern or practice of unconstitutional or unlawful policing."

Leaders in Minneapolis, who praised the decision and pledged their cooperation, can readily attest to the need for such an in-depth investigation. Officers in Minneapolis are seldom disciplined for their actions, well-protected by a powerful union. Chauvin had at least 16 prior complaints against him, only two of which drew reprimands. A recent Star Tribune analysis shows that for the department as a whole, only about 3% of misconduct complaints resulted in discipline.

Although it is difficult to compare because there is no national database, the Seattle Police Department, currently under a federal consent decree, showed 20% of complaints ending in discipline. New Orleans, also under a consent decree, showed 14% of civilian complaints and more than half the number of internal complaints led to discipline.

Chief Medaria Arradondo said he has sought to make reforms for several years, to little avail. Former Police Chief Janeé Harteau in one interview called MPD's discipline system "ineffective." The department's own data shows that since 2008, 60% of use-of-force incidents have been against Black people. And use-of-force incidents have been on the rise, including through 2020.

The state of Minnesota launched its own investigation last June, led by Human Rights Commissioner Rebecca Lucero. Lucero said at the time that the goal was to negotiate a consent decree with the city that courts could enforce. She pointed to a similar decree approved in Chicago after the Justice Department found a long pattern of racially biased policing and excessive force.

Last year, state Public Safety Commissioner John Harrington, a former St. Paul police chief, co-chaired a working group with Minnesota Attorney General Keith Ellison on ways to reduce deadly force by police, along with other reforms.

"There has been a lot of good work done already by communities on the ground, by the state investigators and others," Ellison told an editorial writer on Wednesday. "We look forward to the Justice Department working together with those local groups and the state on systemic change."

Ellison said he took heart from that work and from the officers who stepped up to testify against Chauvin. "They didn't have to do what they did," he said. "They need some help."

That is a point too often lost. There are officers who do their jobs well and fairly, who find themselves in a system that too often protects those who don't. That is just one of many systemic changes that must be made.