MINNEAPOLIS — Derek Chauvin “absolutely” violated Minneapolis Police Department policies and his sworn oath to serve and protect when he knelt on George Floyd’s neck for more than nine minutes, the city’s police chief testified Monday.

During one of the most anticipated moments in the trial, Minneapolis Police Chief Medaria Arradondo unequivocally told the court that Chauvin had failed to follow policies on de-escalation, use of force and offering medical aid to those in need when he ignored Floyd’s cries for help while the man lay pinned beneath his knee.

The use of force should have ended as soon as Floyd stopped resisting, the chief said.

“Once Mr. Floyd had stopped resisting, and certainly once he was in distress and trying to verbalize that, that should have stopped,” Arradondo said.

Clearly when Mr. Floyd was no longer responsive — and even motionless — to continue to apply that level of force to a person proned out, handcuffed behind their back,” Arradondo said, “that in no way, shape or form is anything that is set by policy, is not part of our training, and is certainly not part of our ethics or values.”

Arradondo’s comments came during the start of the second week of testimony in Chauvin’s trial. It was Arradondo who fired Chauvin, a 19-year veteran of the department, after the incident last May.

The chief testified that a Minneapolis resident called him May 25 and asked, “Chief, have you seen the video of your officer choking and killing that man at 38th and Chicago?” It was shortly thereafter that Arradondo reviewed the video that had been shot by a bystander and eventually was viewed by millions of people around the world.

The police chief, who spent hours on the stand meticulously describing department policies and training methods, said the neck restraint that Chauvin used on Floyd was not permitted under rules governing “defensive tactics” that police can use while trying to detain a suspect. He said officers are trained to use “conscious” neck restraints with “light to moderate pressure” but that Chauvin had gone too far.

“When I look at the facial expression of Mr. Floyd, that does not appear in any way, shape or form that is light to moderate pressure,” Arradondo testified.

Arradondo took the stand after days of testimony from other Minneapolis police officers who testified that Chauvin’s use of force on Floyd was excessive and contrary to department training.

On Friday, Lt. Richard Zimmerman, a 35-year veteran who leads the department’s homicide division, called Chauvin’s use of force “totally unnecessary.” He was preceded on the stand by David Pleoger, a recently retired sergeant who was Chauvin’s supervisor in the city’s 3rd Precinct that night, who testified that Chauvin should have stopped kneeling on Floyd’s neck the moment he stopped resisting.

Arradondo, a longtime Minneapolis police officer who became the city’s first Black chief when he took over the department in 2017, fired Chauvin and three other officers the day after Floyd’s May 25, 2020, death.

Floyd’s death and the civil unrest that followed propelled Arradondo into the national spotlight, as he sought to navigate a police department in crisis against the backdrop of a city demanding answers for the death of an unarmed Black man underneath the knee of a White police officer. He met with Floyd’s family and took a knee as the hearse carrying Floyd’s casket arrived in downtown Minneapolis for his funeral.

Arradondo later condemned the actions of Chauvin and the other officers at the scene — J. Alexander Kueng, Thomas K. Lane and Tou Thao — describing Floyd’s death as “murder.”

“Floyd’s tragic death was not due to a lack of training — the training was there,” Arradondo said in a June 2020 statement. “Chauvin knew what he was doing. … What happened to Mr. Floyd was murder.”

Chauvin, at times, appeared uncomfortable during Arradondo's testimony Monday. When the chief was asked to identify Chauvin for the jury, the former officer froze — a pen in his hand, his arm lingering in midair — as Arradondo stood and nodded toward him.

Arradondo’s testimony in Chauvin’s trial has been among the most anticipated moments in the case, in part because it is such an unusual occurrence. It is rare for a police chief to take the stand against one of their officers, experts say.

Prosecutors have struggled to convict police officers, particularly in murder or manslaughter cases. Those prosecutors and some outside experts attribute this to police being given considerable legal latitude to use force as well as jurors’ hesitation to convict officers on the most serious counts. They also say jurors and judges tend to find police officers trustworthy.

Chauvin is charged with second- and third-degree murder and second-degree manslaughter in Floyd’s death. The other three officers are charged with aiding and abetting murder and manslaughter.

Arradondo’s testimony, along with that of other officers, seems aimed at undermining the defense’s claims that Chauvin was following his training and using needed force when he knelt on Floyd. Having Arradondo, a sitting police chief, testify in uniform gives the prosecution a powerful witness — one who effectively can speak on behalf of the city’s entire police department — regardless of whether he intends to be seen that way.

“If the jury sees Chauvin as the defense is trying to portray him, as simply doing what he was trained to do as a police officer, it would be nearly impossible for them to find that he intended to harm Mr. Floyd, a finding necessary for a second-degree murder conviction,” Craig B. Futterman, a law professor at the University of Chicago and director of the Civil Rights and Police Accountability Project, said in an email.

“The prosecution’s testimony from high ranking officers … provides a powerful counterweight to the defense argument,” he said.

Futterman and other experts could not recall many comparable cases of a chief testifying. “Not only is such testimony relatively rare as a result of the police code of silence, it has been highly effective, in my opinion,” Futterman added.

Arradondo told the court that he learned what had happened that night when another officer called him at home about a “critical incident." Arradondo called the mayor and headed to City Hall, where he viewed video from a police security camera mounted at 38th and Chicago.

The chief, who throughout his testimony sat with his body toward members of the jury and spoke to them almost as a storyteller, recalled how nothing in that initial video had “jumped out” or alarmed him. But a few hours later, Arradondo received a message from a “community member” about the now-viral bystander video of Floyd’s arrest.

Arradondo was followed on the stand by Inspector Katie Blackwell, who commands the city’s 5th Precinct but once oversaw the department’s training program.

Blackwell, a longtime officer and one of the few women in a senior position in the department, testified that she first met Chauvin 20 years ago when they worked together as community service officers — the precursor to being hired as a police officer. She said she later hired Chauvin to be a field training officer.

Blackwell testified that Minneapolis Police Department officers are trained to use “one arm or two arms” for neck restraints. Presented with a still photo of Chauvin kneeling on Floyd’s neck, Blackwell said the maneuver Chauvin was using on Floyd was not department training.

“I don’t know what kind of improvised position that is,” Blackwell testified. “That’s not what we train.”

The day began with testimony from Bradford Langenfeld, an emergency medicine physician who spent at least a half-hour trying to revive Floyd when he was taken to Hennepin County Medical Center. It was Langenfeld who later pronounced Floyd dead.

Langenfeld, who is now practicing medicine in northern Minnesota, testified that Floyd arrived at the hospital in cardiac arrest and upon further examination was showing “pulseless electrical activity.” One of the most common causes of “PEA” status, Langenfeld testified, is hypoxia or “low oxygen.”

The doctor testified that he was told by paramedics that they had tried to revive the man for about 30 minutes before he was brought to the hospital, but heard of no other lifesaving efforts at the scene, including by police. He described Floyd’s body being hooked up to machines to try to resuscitate him but said he never saw the man’s heart beat on its own, “not to a degree sufficient to sustain life.”

Langenfeld said he declared Floyd dead a half-hour later. “There was virtually no cardiac activity,” he told the jury. “I determined the likelihood of any meaningful outcome was far below 1 percent and that we would not be able to resuscitate Mr. Floyd.”

Asked about his “leading theories” as to why Floyd had died, Langenfeld said he considered “excited delirium” — a controversial medical term used to describe the sudden in-custody death of people who may be under the influence of drugs or in an agitated state. One of the officers who was restraining Floyd — Lane — mentioned the term at the scene, and Chauvin’s defense is expected to address the theory its in case.

But Langenfeld said he ruled out “excited delirium” because there was “no report that the patient was ever very sweaty” — which he described as one of the symptoms. Pressed further by prosecutors about what he thought had caused Floyd’s death, Langenfeld said he believed, based on what he knew at the time, that low oxygen was “one of the more likely possibilities.”

“Is there another name for death by oxygen deficiency?” prosecutor Jerry Blackwell asked.

“Asphyxia,” Langenfeld replied.

During cross-examination, Eric Nelson, Chauvin’s defense attorney, pressed the doctor on whether drugs such as fentanyl and methamphetamine — two substances found in Floyd’s body, according to his autopsy — could lead to a lack of oxygen in the body. “That’s correct,” Langenfeld replied.

Abigail Hauslohner contributed to this report.