The trial of a former Minneapolis police officer in George Floyd's death is expected to turn toward the officer's training on Monday after a first week that was dominated by emotional testimony from eyewitnesses and devastating video of Floyd's arrest.

Floyd had no pulse when he arrived and was in cardiac arrest, which Langenfeld described as the "sudden cessation of blood flow to all the tissues of the body when the heart stops pumping".

Also testifying on Monday was the doctor who treated Floyd when he was brought to the emergency room at the Hennepin County Medical Center. Asked by prosecutor Jerry Blackwell if the paramedics indicated that they suspected a drug overdose or heart attack, Langenfeld said they did not, indicating only that Floyd's heart had stopped beating and that there may have been a delay in starting resuscitation efforts.

The 45-year-old Chauvin, who is white, was seen in a video taken by a bystander kneeling on the neck of a handcuffed Floyd for more than nine minutes as the 46-year-old African-American man complained repeatedly that he "can't breathe".

He has pleaded not guilty to murder and manslaughter charges in the case being heard by a racially diverse 12-member jury.

Chauvin lawyer Eric Nelson questioned Langenfeld about whether some drugs can cause hypoxia, or insufficient oxygen. An autopsy found fentanyl and methamphetamine in Floyd's system.

The county medical examiner's office ultimately classified Floyd's death a homicide - that is, a death at the hands of someone else.

Chauvin did not follow his training in several different ways, Arradondo said. The defense argues that Chauvin did what he was trained to do and that Floyd's use of drugs and underlying health conditions caused his death.

Dr Lagenfeld told the court he believed that Mr Floyd's death was caused from a lack of oxygen, called asphyxia. But on questioning from the prosecutor, the doctor said the high levels were also consistent with cardiac arrest.

Officers carry tourniquets and are trained how to use them to treat gunshot wounds, they are taught how to do chest compressions, and they are given naloxone inhalers that can be used to rapidly reverse an opioid overdose, Arradondo said. The doctor said giving Narcan once a patient is in cardiac arrest would provide no benefit.

Floyd's treatment by police was captured on widely seen bystander video that soon sparked protests that rocked Minneapolis and quickly spread to other USA cities and beyond.

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Dr Langenfeld told the court, "Any amount of time that a patient spends in cardiac arrest without CPR markedly decreases the chances of survival" before explaining that those chances dropped by 10 to 15 percent with each passing minute.

"We put a lot of time, energy and resources into our training", Arradondo said, adding that roughly $8.5 million was spent training in their budget.

Chauvin is now on trial for the murder of Floyd in Minneapolis, a trial which is surrounded by controversy.

Prosecutor Steve Schleicher noted that while some people may become more unsafe under the influence of drugs or alcohol, some may actually be "more vulnerable".

"It's recognizing that when we get the call from our communities, it may not often be their best day, and they may be experiencing something that's very traumatic", the chief said. Another said Chauvin never eased up, either by putting a hand on the ground or leaning on a squad auto next to him.

After walking through the levels of training recruits, cadets and ongoing training officers receive, Chief Arradondo was asked to quantify how much training officers get in his department.

Instead, officers continued to restrain Floyd until an ambulance arrived - even after he became unresponsive.

The officers also rebuffed offers of help from an off-duty Minneapolis firefighter who wanted to administer aid or tell officers how to do it.

Testimony in the trial concluded for the week on Friday when two Minneapolis police officers criticized Chauvin's actions during the arrest of Floyd. "Chauvin knew what he was doing".

Footage of Mr Chauvin kneeling on Mr Floyd's neck was viewed around the world and sparked mass demonstrations against racism and police brutality.

Prosecutors previously called supervisory officers to build the case that Chauvin improperly restrained Floyd. A duty sergeant and a lieutenant who leads the homicide division both questioned Chauvin's actions in pinning Floyd after officers responded to a report that Floyd had passed a counterfeit $20 bill.