The head of the Minneapolis Police Department discussed training and de-escalation techniques on the witness stand on Monday at the trial of the former police officer accused of killing George Floyd.

Police chief Medaria Arradondo, 54, fired Derek Chauvin and the three other officers involved in the May 25, 2020 arrest that led to Floyd's death, within days of the incident.

Chauvin, who is white, was seen in a video taken by a bystander kneeling on the neck of a handcuffed Floyd, a 46-year-old black man, for nearly nine minutes.

The video touched off protests against racial injustice and police brutality in the US and around the world.

Chauvin, 45, has pleaded not guilty to charges of murder and manslaughter.

The first five days of his trial featured emotional testimony from bystanders who witnessed Floyd's arrest and repeatedly urged Chauvin to remove his knee from Floyd's neck.

Arradondo was questioned extensively on Monday by prosecutor Steve Schleicher about the training his officers receive in de-escalation techniques designed to prevent the use of force.

"We put a lot of time, energy and resources into our training," he said. "Training is absolutely, vitally essential to us as a department."

He was also asked about the code of ethics followed by Minneapolis police officers and the department's "professional policing policy."

Arradondo, who joined the Minneapolis Police Department in 1989 and worked his way up through the ranks, described it as "treating people with dignity and respect."

The police chief described de-escalation as a set of skills needed to "stabilize a situation."

"The goal is having a safe and peaceful outcome," he said.

Schleicher did not ask the police chief specific questions about Floyd's arrest but was setting the stage to do so after a lunch break.

Arradondo has previously described Floyd's death as a "murder."

This screenshot obtained from pool video feed via Court TV on April 5, 2021, shows Minneapolis Police Chief Medaria Arradondo testifying during the trial of former police officer Derek Chauvin charged in the death of George Floyd in Minneapolis, Minnesota. Photo: AFP

'Hypoxia'

Also testifying on Monday was the doctor who treated Floyd when he was brought to the emergency room at the Hennepin County Medical Center.

Dr Bradford Wankhede Langenfeld said Floyd was in cardiac arrest when he arrived and 30 minutes of efforts to revive him were unsuccessful.

He said a lack of oxygen was the most likely reason Floyd's heart had stopped beating.

"I felt that hypoxia was one of the more likely possibilities," Langenfeld said.

Prosecutors are seeking to prove that Floyd's death was due to asphyxiation while Chauvin's defence attorney claims it was due to illegal drugs in his system.

Langenfeld said the two paramedics who brought Floyd to the hospital did not mention any drug use or the possibility that he had overdosed.

The longest-serving officer in the Minneapolis Police Department testified last week that Chauvin's use of force against Floyd was "totally unnecessary."

Lieutenant Richard Zimmerman said he had reviewed bystander and police bodycam video of Floyd's arrest and Chauvin had violated department policies on the use of force.

"Pulling him down to the ground facedown and putting your knee on a neck for that amount of time, it's just uncalled for," Zimmerman said.

Besides listening to the testimony of police officers and witnesses, the nine-woman, five-man jury hearing the case in a heavily guarded Minneapolis courtroom has been shown the graphic video of Floyd's arrest.

Chauvin faces up to 40 years in prison if convicted of the most serious charge - second-degree murder.

The other three former police officers involved in the arrest - Tou Thao, Thomas Lane, and J Alexander Kueng - are to be tried separately later this year.