Minneapolis Police Chief Medaria Arradondo testified Monday that fired officer Derek Chauvin used excessive force and defied his own training and the department's mission of compassion when he knelt on George Floyd's neck as Floyd pleaded for his life.

Arradondo's testimony came amid a consistent voice of disapproval from key department leaders that began last week with similar statements from the head of the homicide unit. Testimony wrapped Monday with the department's former head of training, who echoed Arradondo's sentiments.

"Once Mr. Floyd had stopped resisting — and certainly once he was in distress and trying to verbalize that — that should have stopped," Arradondo said after recounting department policy on when to use force vs. de-escalation tactics.

"There's an initial reasonableness of trying to just get him under control in the first few seconds," the chief said, "but once there was no longer any resistance, and 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, that in no way shape or form is anything that is by policy, part of our training and is certainly not part of our ethics or values."

Chauvin's attorney, Eric Nelson, raised several key defenses in his cross-examination of Arradondo, who agreed that officers can use force sometimes to de-escalate a situation, neck restraint techniques were permitted by the department at the time, and handcuffed suspects can inflict harm.

Nelson pointedly asked the chief when he last arrested a suspect.

"It's been many years, sir," Arradondo said.

Under cross-examination, the chief also agreed that department policy affords an officer flexibility between using force and choosing to de-escalate an encounter with someone resisting arrest.

Chauvin is on trial on charges of second-degree murder, third-degree murder and second-degree manslaughter in Floyd's May 25 death.

Prosecutors on Monday also began introducing cause of death evidence through their questioning of the Hennepin County Medical Center doctor who treated Floyd and declared him dead. Dr. Bradford Wankhede Langenfeld, who testified first thing Monday, said that upon arrival Floyd did not have a heartbeat "sufficient to sustain life" and that his cardiac arrest was due to a lack of oxygen.

"Is there another term for that?" asked prosecutor Jerry Blackwell.

"Asphyxia," said Langenfeld, who was a senior medical resident at the time.

Langenfeld testified that Floyd didn't have a pulse but showed some electrical activity.

The cause of death is poised to become a potentially complex and confusing issue for jurors to decipher. Prosecutors plan to prove Floyd died of asphyxiation despite the Hennepin County medical examiner's ruling that he died of "cardiopulmonary arrest complicating law enforcement subdual, restraint, and neck compression."

Nelson has argued that Floyd likely died of a drug overdose and pre-existing health issues, including heart disease.

Arradondo testified next, recounting how a deputy chief called him about 9 p.m. last spring to report an arrest that resulted in a civilian being transported to the hospital. The chief said he was told the person was still alive.

Arradondo contacted the Minnesota Bureau of Criminal Apprehension, which investigates critical incidents involving police, and Mayor Jacob Frey. He then departed for his office downtown.

The chief said he reviewed city surveillance video of the incident but nothing "jumped out at me," because the video had no audio and because the four officers' backs were turned to the camera located across the street. Floyd was largely obscured by the officers.

It was close to midnight when Arradondo received a call from a community member. "Chief," Arradondo testified he was told, "have you seen the video of your officer choking and killing that man at 38th and Chicago?"

"And so once I heard that statement I just knew it wasn't the same … video that I saw," Arradondo said.

Minutes later he watched the video recorded by bystander Darnella Frazier, then 17, who is credited by many for prompting the four officers' prosecution by sharing an independent, close-up perspective of the arrest.

Prosecutor Steve Schleicher asked Arradondo if Chauvin's conduct adhered to the department's policy on de-escalation.

"I absolutely do not agree with that, that action is not de-escalation," he said. "When we talk about the framework of our sanctity of life and we talk about the principles and values we have, that action goes contrary to what we're talking about."

The chief's assessment during several hours on the witness stand complemented testimony last week from veteran police Lt. Richard Zimmerman, the head of homicide who called Chauvin's actions "uncalled for."

Nelson underscored the dangers of police work and highlighted Arradondo's remove from street-level policing in his cross-examination. He instructed Arradondo to read part of the department's use-of-force policy and asked if it defined active resistance, in part, as suspects pulling away, hiding their arms or making statements to avoid arrest.

Yes, the chief said.

Nelson has argued that Floyd was resisting arrest and posed a possible safety risk to his client and the other officers at the scene — J. Alexander Kueng, Thomas Lane and Tou Thao. The other three are scheduled to be tried Aug. 23. All four defendants, who were fired, are out on bond.

"Sometimes an officer has to command the presence; they have to take control of the situation?" Nelson asked, noting that department policy allows the use of a weapon in some circumstances as part of de-escalation.

"Yes," the chief said.

The two went back and forth a few rounds on the same issue when Nelson asked a hypothetical: If an officer decided to use a hobble restraint that binds the ankles to the waist but then backed away from it, would that be moving "backwards down the continuum of use-of-force?"

Yes, the chief eventually said.

The officers at Floyd's arrest had considered using the hobble restraint, which requires calling a supervisor to the scene due to the risk of positional asphyxia, and opted not to.

Nelson also introduced the concept of "camera perspective bias" by playing a clip of Frazier's video that appeared to show Chauvin kneeling on Floyd's neck and then playing a clip of Kueng's body-worn camera from the same time frame that appeared to show Chauvin kneeling on Floyd's shoulder. He also showed them together in a split screen.

Arradondo testified that the Kueng video showed Chauvin kneeling on Floyd's shoulder.

On redirect, Schleicher did not challenge the cameras' different perspectives, but asked the chief if Chauvin knelt on Floyd's neck up until the several-seconds-long video clips in question, which came at the end of the arrest when paramedics arrived.

Yes, Arradondo said. Schleicher showed him an image taken from Frazier's video that depicted Chauvin kneeling on Floyd's neck. Arradondo said it was not a trained technique at Minneapolis police.

In an attempt to discredit Nelson's argument that angry bystanders posed a safety risk to the officers, Schleicher showed Arradondo the picture again and asked, "Would one way to de-escalate the crowd who's experiencing something shocking [is] to stop doing the thing that's shocking them?"

"Absolutely," the chief said.

"I have nothing further," Schleicher said.

Prosecutors later showed the same picture to Minneapolis police inspector Katie Blackwell, who ran the department's training division until recently.

"I don't know what kind of improvised position that is," she said, "So, it's not what we train."

Court resumes at 8:30 a.m. Tuesday with attorneys and Hennepin County District Judge Peter Cahill discussing a motion filed by potential witness Morries Hall. Hall was in the car with Floyd outside of Cup Foods when police approached to investigate a reported fake bill.

Hall filed a motion last week invoking his Fifth Amendment right against self-incrimination and asked the court to quash a subpoena requiring him to testify if he is called. Cahill on Monday signed an order allowing Hall to wear civilian clothes instead of jail scrubs for the court appearance. Hall is in custody on an unrelated matter.