A Minneapolis police officer at the center of two police brutality lawsuits that have cost the city more than $400,000 has also been investigated more than a dozen times. Yet so far, Officer Michael Griffin has never been disciplined.

Critics say Griffin's case raises questions about the city's system of oversight and discipline for officers.

• Related: Wearable cameras for Minneapolis police?

In May of last year, Griffin was one of more than a dozen police officers given the Medal of Valor for his response to the mass shooting at Accent Signage in September of 2012. "All fell back on their training, overcame the horrific scene and moved into the building, into the unknown," said Lt. David Hayhoe when he announced the names of the award winners.

Griffin and his fellow officers walked into the worst mass shooting in the city's history. Six people, plus the shooter, were killed. Three others were wounded. Griffin's public personnel file also contains an Award of Commendation in 2009 after Griffin helped chase down an armed suspect.

Yet during his nearly eight years on the force, Griffin has been the subject of 18 investigations by either the Internal Affairs Unit, the city's former Civilian Review Authority or the new Office of Police Conduct Review. Three of the cases have not been resolved yet. Under state data practices law, the allegations contained in those complaints are private.

But in one case, court documents show that in the early morning hours of May 29, 2010, Ibrahim Regai claims Griffin -- who was not in uniform and not on duty -- punched him and knocked him out. Regai, 39, alleged the altercation outside a downtown Minneapolis nightclub happened after an argument.

Regai sued Griffin and the city, and reached a settlement with the city earlier this year for $140,000.

"We have, every day, people are getting beat up and abused. And every year we're getting millions in lawsuits," said Dave Bicking, who served on the city's Civilian Review Authority, which has now been replaced by the Office of Police Conduct Review. He has observed all seven monthly meetings of the civilian commission that oversees the new body. Bicking says so far, that relatively new system has failed to hold officers accountable.

"If officers are supposed to have any deterrence through discipline, that discipline has to come in a reasonable timely fashion. And they really have stepped up the time -- the quickness of processing the cases. But if the result of the process is nothing, why there's no timely discipline anyway," Bicking said.

According to a recent city report, some of the officer complaints referred to precinct supervisors for 'coaching' are taking too long to resolve. Coaching is a process designed to provide intervention between an officer accused of a low level infraction and his or her supervisor within 45 days. However, in two precincts, the average age of outstanding or completed coaching cases is nearly 250 days. Some precincts have made progress. The same statistics show three precincts have cleared all of their outstanding coaching cases.

The Office of Police Conduct Review has received 570 complaints since the fall of 2012. A few dozen of those have made it through the triage and investigation process, and landed on Chief Janee Harteau's desk. Between Sept. 2012 and March of this year, the OPCR has received 570 complaints. Most of those cases have either been dismissed or referred directly to the coaching process. A review panel made up of sworn officers and civilians determine which cases go forward to Harteau for a final determination. The complaints can contain allegations against an officer that the review panel has determined have merit or no merit. Michael Browne, director of the Office of Police Conduct Review, says Harteau has made disciplinary decisions in all the cases that made it to her desk in the first three months of this year.

So far, the chief has disciplined officers with letters of reprimand and suspensions in just four of those cases.

"We do not have control over what the chief does with the cases once they are referred from the review panel," said Michael Browne, director of the Office of Police Conduct Review. Browne rejects criticism that the new civilian oversight body has been ineffective. He said state law prohibits civilian authorities from making recommendations on discipline to police chiefs. Members of the oversight commission simply review complaints and make recommendations about police training and policies.

"I think that that's where they're going to be able to make the largest impact. To be able to affect what's happening, from a policy perspective," he said.

Each month the commission posts three case summaries online that will be discussed at the next meeting. Browne says that transparency is one of several improvements over the previous system. He says the emphasis on coaching officers frees up the case load for investigators to look into more serious allegations.

Minneapolis police officials won't comment on specific investigations, and declined to comment on whether or not the number of complaints against Officer Michael Griffin is excessive.

Attorney Gregg Corwin, who's represented several police officers who've been fired and want their jobs back, says the number of complaints against an officer is often influenced by when and where the officer works.

"If it's a high crime area and they're there during a time period when crime spikes, they're going to be involved in more incidents and therefore subject themselves to more complaints."

Griffin has spent most of his career working on the north side in the Fourth Precinct, which contains some of the most violent hot spots in the city.

Corwin is representing former Minneapolis police officers Shawn Powell and Brian Thole. He says the two men were unfairly fired after they were video taped last year by Green Bay police officers allegedly using racial slurs. Harteau has refused to talk about what disciplinary action she took. But she said at the time the videotape was released that she was appalled by what she saw.

Police officials are exploring the prospect of equipping officers with body cameras, as a way to reduce misconduct complaints and lawsuits. An MPR News analysis of data from the Minneapolis City Attorney shows the city has paid out more than $21 million to resolve misconduct lawsuits and claims during the last decade.