While a police K-9 tore into Frank Baker's shin, St. Paul officer Brett Palkowitsch kicked him in the ribs twice, breaking them. Then he kicked him again, and act that evoked "disgust and anger," one of his colleagues at the scene would go on to testify in federal court.

A jury heard opening statements Wednesday morning in a trial in St. Paul that will determine if Palkowitsch should be held criminally liable for violating Baker's civil rights, or if the officer was justified in using force to bring what he believed to be a dangerous suspect into compliance.

The case, stemming from the June 2016 arrest, marks a rare example of a police officer being charged criminally for using force on duty. Along with graphic squad car dashcam footage which captured the incident, much of federal prosecutors' case relies on the testimony of Palkowitsch's colleagues, including two officers who have since left the department.

Palkowitsch, 32, was indicted in January on one count of deprivation of rights in connection with the incident, which left Baker with seven broken ribs and two collapsed lungs. The city settled a lawsuit with Baker for a record $2 million. Palkowitsch remains on paid administrative leave pending the outcome of the case. Chief Todd Axtell fired Palkowitsch, going beyond the discipline recommended by the Police Civilian Internal Affairs Review Commission, but by law had to rehire him after an arbitrator ruled in 2017 that he should get his job back.

On June 24, St. Paul officers responded to an unnamed 911 caller reporting of a violent street fight near an apartment building on St. Paul's East Side. The caller said one man, who he described as African-American with dread locks and a white T-shirt, was carrying a gun. Baker matched the description but was unarmed and not involved.

Officers Joseph Dick and Anthony Spencer, both of whom have left the department, were the first to arrive on scene. They found no evidence of a violent mob, which Dick reported back to dispatch and the other squads en route. They saw Baker in a white Jeep in a parking lot nearby, but didn't deem him a threat.

Dick, who now works for the FBI, testified that he didn't like Palkowitsch's policing style, and he'd seen Palkowitsch escalate situations in the past. When he arrived on scene and saw no mob, Dick said, he made sure to report to dispatch promptly because he knew Palkowitsch was en route.

Dick told the court he felt "disgust and anger" after seeing Palkowitsch repeatedly kick Baker, in what he described as unjustified use of force.

Afterward, Dick said, Palkowitsch approached him and asked, "Hey, what are we going to arrest this guy for?"

Dick said he took this to mean Palkowitsch wanted him to help corroborate a story, which "was not going to happen." Dick rode with Baker to the hospital, and later came back to the precinct to confront Palkowitsch.

Dick said he couldn't sleep that night. The next day, he wrote an e-mail from his official account to his supervisor, Sgt. Brian Murphy, saying he was concerned about what happened and wanted to meet. Dick said Murphy replied with a text message to his personal cellphone, which Dick interpreted as Murphy not wanting to create an official record of the exchange.

Dick said his complaints fell "on deaf ears" in the department, and internal affairs didn't interview him about the incident. He said deciding to testify against a fellow officer was "one of the hardest things I've had to do."

K-9 Officer Brian Ficcadenti was suspended for 30 days for his role in the incident. He and Falco were also removed from the K-9 unit. Dash camera video played in the courtroom showed Falco lunge toward Baker and take him to the ground, prompting Baker to scream in pain repeatedly.

Officers can be heard shouting commands while the dog mangles Baker's leg.

"Don't move!" "Turn over!" "Get your hands up right now!"

After Palkowitsch kicks Baker, two officers carry him to the squad car, where Dick calls for a medic.

"I can't breathe!" Baker screams.

In court, Palkowitsch's attorneys said their client arrived to find the K-9 biting what he had reason to believe was a dangerous suspect. Ficcadenti lost control of the situation, they said, and when Baker failed to comply with the officers' commands, Palkowitsch applied "calculated foot strikes."

"He was not taught that you cannot kick," defense attorney Deborah Ellis said.

The prosecutors say Palkowitsch explicitly violated training, which instructs officers not to intervene when a K-9 has been deployed onto a suspect. Instead, Palkowitsch shouted orders that in some cases conflicted with Ficcadenti's, making it impossible for Baker to comply.

Palkowitsch later boasted about kicking Baker to fellow officers, said Assistant U.S. Attorney Zachary Dembo.

He also sent a photo of Baker in the hospital to Rachelle Erickson, a fellow officer, with a text saying he'd broken the man's ribs. In court, Erickson said the text confused her. "I just remember thinking he was bragging," she said.

Staff writer Chao Xiong contributed to this report