As he readies for the second half of an already tumultuous term, Seattle Mayor Mike McGinn has been confronted with perhaps his most difficult test yet: how to respond to the U.S. Department of Justice report accusing police of routine use of excessive force.

McGinn must navigate between police, who have reacted with skepticism to the findings, and community groups calling for a sweeping overhaul of the Police Department, saying the DOJ report vindicates their longstanding complaints about officer conduct.

That's a tall order for the former Sierra Club leader and attorney who ran for office in 2009 talking more about the folly of a downtown tunnel than overseeing a police force.

"He'd never had any experience in public safety," said former City Councilmember Jan Drago.

The issues raised by the DOJ report predate McGinn, Drago noted. "It's an entrenched problem that's been ongoing for years. It's been raised over and over again and hasn't been resolved."

In an interview Saturday, McGinn spoke cautiously, neither repudiating nor embracing the DOJ's overarching findings.

"This is a big deal about the type of police force we have and want to have, so we have to be deliberative and thoughtful," McGinn said, adding that concerns over use of force had been "a high priority" since he took office.

He repeated that the city will seek more information on how the DOJ reached its conclusions when the two parties meet next month. "If we are going to be talking to our police officers on how to do things differently, we need to have a thorough understanding from DOJ on the practices they found inappropriate."

McGinn said he was focused on "outcomes," vowing to work toward a Police Department that is "effective" and has "a strong sense of trust with the community."

The federal report was a rebuke to police brass, including Police Chief John Diaz, the 30-year Seattle Police Department veteran whom McGinn chose to lead the department last year despite calls by some to bring in an outsider.

The report said "starting from the top, SPD supervisors often fail to meet their responsibility to provide true oversight of the use of force."

While stressing most police officers are not a problem, the report said a small number are too quick to "escalate" situations — unnecessarily pummeling people with nightsticks, punching or pepper spraying them.

Diaz resisted the DOJ findings on Friday, saying his staff has reviewed his officers' use of force and didn't reach the same conclusions. He also demanded more information on how DOJ justified its findings.

McGinn has backed that approach, continuing to refer to the DOJ findings as "allegations" in a statement on his website.

Jordan Royer, who was public-safety adviser to former Mayor Greg Nickels, urged McGinn to dispute the DOJ findings, calling the investigation a "hatchet job."

"I think the mayor should fight this in court. I think they have a weak case," Royer said, warning that the report could harm police morale and lead to officers being less proactive on the streets. "At the end of the day, I don't see anything good coming of this."

But critics of SPD leadership see the DOJ findings as more reason to replace Diaz and bring fresh talent to the department.

"I really personally feel he needs to fire Diaz and clean house," said Pat Murakami, president of the Southeast Seattle Crime Prevention Council, who had opposed Diaz's hiring as chief.

"There is a difference between proper preventive policing and excessive use of force. You do not have to get aggressive and rude even with the criminals," Murakami said.

In Saturday's interview, McGinn defended Diaz, saying he chose him because "he believes in having a highly professional police force." McGinn added that Diaz "has not hesitated to impose appropriate discipline" on officers who fall short of that standard.

Police union leaders noted that any changes that affect officers would have to be bargained during contract negotiations. Those negotiations are ongoing, and McGinn said he has been factoring in possible changes resulting from the DOJ probe into those talks.

City Council members warned that it would be a mistake for the city to dispute the DOJ findings.

"I don't think our time is best spent arguing the details of the DOJ report," said Councilmember Sally Clark.

"The wise thing to do is to receive these findings as constructive criticism and to begin the process of systematic reform in the Police Department," said Councilmember Tim Burgess, who chairs the council's Public Safety and Education Committee.

Though he is frequently mentioned as a likely challenger to McGinn in 2013, Burgess declined to criticize the mayor's response to the DOJ report.

"I'm not going to evaluate the mayor or critique his performance in office," Burgess said, adding that he and McGinn "work well together and will continue to do so."

Councilmember Nick Licata said he agrees with McGinn's request for more information from the DOJ.

But Licata said the controversy could be a blessing for a mayor badly in need of victories. McGinn likely will face an uphill battle and several notable challengers if he runs for re-election.

"He could help himself if he took a strong position on this. He has an opportunity here to show he is a mayor that can lead and create positive change," Licata said.

Jim Brunner: 206-515-5628 or jbrunner@seattletimes.com On Twitter @Jim_Brunner.