Like all of his colleagues, Michael Griffin took an oath to protect and serve when he joined the Minneapolis Police Department. Federal prosecutors contend that he abused his power as a cop, including lying about assaulting four men on separate occasions.

Nearly a year after Griffin was first indicted on nine criminal counts, prosecution and defense lawyers presented their opening statements Tuesday at his jury trial in U.S. District Court in St. Paul.

Assistant U.S. Attorney Manda Sertich sought to cast Griffin as a rogue cop who tried to hide behind his badge after separate altercations — one in which he pummeled a man unconscious outside the Envy Nightclub, and another about 18 months later at the Loop Bar. Prosecutors contend that both times he falsified reports and lied during sworn testimony in lawsuits stemming from the confrontations.

"He knows the magic words that he needs to use in police reports to justify use of force," Sertich said to the jury of eight men and six women, including two alternates. In at least one of the confrontations, she said, Griffin, who was off-duty and in plain clothes, pulled out his badge to gain a "tactical advantage."

"Why did he pull out his badge? To trigger the respect that most people have for police officers, because everybody knows that you don't fight police officers," Sertich contended.

The defense disputed that characterization, saying that in both instances the men, emboldened by "alcohol and testosterone" forced Griffin to use force in self-defense. Griffin's attorney, Robert Richman, suggested that race played a significant role in the Loop incident, in which a mixed-race group of men singled out and tried to provoke Griffin after learning that he was a police officer and because he was black.

Richman showed the jurors, four of whom are black, a portion of the transcript of a 911 call made by one of the men involved in the Loop case, who referred to Griffin as "a black" who "looks like a bitch."

Punched to the ground

Griffin faces nine counts in an indictment that charges him with depriving the men of their civil rights, falsifying reports and committing perjury in testimony in two brutality lawsuits filed against him. He has pleaded not guilty to all the charges. Griffin remains on home assignment after being relieved of duty.

The two confrontations that form the backbone of the prosecution's case occurred 18 months apart.

In the first, laid out by prosecutors in court Tuesday, Griffin is alleged to have confronted and knocked out Ibrahim Regai outside Envy. Sometime after the bar closed on May 29, 2010, they said, Regai was leaving Aqua, a nightclub in the Warehouse District after a night of partying with two female friends — one of whom was the wife of Griffin's close friend.

Griffin and the woman's husband happened to be in the area, according to court testimony, when they saw Regai and the two women. An argument ensued between the husband and wife, which led to a heated exchange between the husband and Regai, who intervened without realizing that the two were married. After the two men were separated, Regai walked half a block down to Envy, but returned and resumed arguing with Griffin's friend. Griffin intervened by pulling out his badge and telling Regai to leave. Regai later told investigators that he didn't believe Griffin was a cop.

As Regai turned to walk back to Envy, prosecutors say, Griffin followed and confronted him outside the club. Moments later, Regai was lying unconscious on the sidewalk. Prosecutors said that Griffin wrote a police report that falsely claimed Regai had instigated the confrontation, and again lied about his role in it to FBI agents.

Security camera footage played in court appears to show Griffin knocking Regai to the ground with a punch, and then a crowd forming around the two men. Regai, who said he blacked out for about 30 seconds, testified Tuesday that he went to a hospital that night for stitches to close a large gash on the back of his head from where he hit the sidewalk, as well as a split lip.

During his cross-examination, Richman tried to poke holes into Regai's credibility as a witness, pointing out that the Somali national had lied to immigration officials after entering the country on falsified documents and had a history of cocaine use.

In the second altercation, on Nov. 5, 2011, prosecutors allege Griffin confronted four men — Jeremy Axel, Matthew Mitchell, Keyon Cooley and another man at the Loop Bar. Prosecutors allege that Griffin grabbed Cooley outside the bar, "flipped him to the ground … kicked [Mitchell] in the chest and punched [Axel] in the head from behind, rendering [him] unconscious." When police arrived, Griffin gave "false, incomplete and misleading information, resulting in Mitchell being arrested for obstructing a police officer with force," the indictment said.

Those witnesses will be called to testify later in the two-week trial.

Throughout the proceedings, Richman contended that the other men in both instances were the aggressors.

"These men fueled by testosterone and alcohol were dead set on teaching officer Griffin a lesson," he told jurors.

Griffin, who joined the force in 2006 and was once considered a rising star, has numerous department citations, including the medal of commendation for confronting four gunman during a shootout outside the Fourth Precinct headquarters, and a Medal of Honor for his role in the police response to the 2012 mass shooting at Accent Signage.

But Griffin, who has worked mostly in the Second and Fourth precincts, has also been the subject of 22 civilian complaints. Only one of the complaints was sustained.

He is expected to testify during the 10-day trial.

In a flurry of pretrial motions and counter-motions, both sides argued over whether the prosecution could tell jurors about a 2009 incident in which Griffin was accused of pepper-spraying an unruly drug suspect in the back of his squad car.

Also at issue was whether the men Griffin is accused of assaulting could be referred to as victims in court. U.S. District Judge Donovan Frank ruled that the prosecution could only call them victims in opening and closing arguments.