Lt. Johnny Mercil became the latest member of the Minneapolis police force to testify as part of an effort by prosecutors to dismantle the argument that Chauvin was doing what he was trained to do when he put his knee on George Floyd's neck last May.
Prosecutors are seeking to prove that Floyd's death was due to asphyxiation, while Chauvin's defense claims it was due to illegal drugs in Floyd's system.
Chauvin has argued he followed police training when he kept his knee pushed into Floyd's neck for more than nine minutes on 25 May 2020, as the handcuffed 46-year-old man fell limp and stopped breathing.
Footage of Mr Chauvin kneeling on Mr Floyd's neck was viewed around the world and sparked mass demonstrations against racism and police brutality.
No witnesses at the scene were arrested, and several of them have testified that they urged officers to check Mr Floyd's pulse and provide him with medical care.
Sgt Jody Stiger, a use of force expert for the Los Angeles Police Department, testified that officers were initially justified in their actions because Mr Floyd was "actively resisting" arrest as he was being placed in the patrol vehicle.
Mr Mercil testified that based on the training that officers receive, Mr Chauvin should only have used that manner of neck restraint if there was "active aggression" involved.
Prosecutor Steve Schleicher noted that while some people may become more risky under the influence of drugs or alcohol, some may actually be "more vulnerable". Hall's attorney contends that anything Hall says about his alleged drug activity with Floyd could leave him vulnerable to being charged with third-degree murder. He repeatedly said he was claustrophobic.
The judge said he would rule later on Hall's request not to testify. As long as they do not obstruct police, onlookers "have the absolute First Amendment rights to record", he said.
Officers continued to restrain Mr Floyd - with Chauvin kneeling on his neck, another kneeling on Mr Floyd's back and a third holding his feet - until the ambulance got there, even after he became unresponsive, according to testimony and video footage.
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.
He asked whether officers need to take the actions of a crowd into account, police chief Arradondo agreed.
During that time, Morries Lester Hall, a key witness who was with George Floyd on the day he died, will appear remotely from the Hennepin County jail.
But prosecutors quickly got Mr Arradondo to note that the clip played by Nelson depicted only the few seconds before Floyd was moved onto a stretcher. In June, he called Floyd's death a "murder" in response to an inquiry from the Minneapolis Star Tribune.
She said Chauvin also was a field-training officer, receiving additional training so he would know what prospective officers were learning in the academy.
Schleicher showed a still image taken from bystander video of Chauvin with his knee on Floyd's neck - one that jurors have seen several times - and asked Mercil: "Is this a use of force?"
Under cross-examination by Chauvin attorney Eric Nelson, Mercil testified that officers are trained to use their knee across a person's back or shoulder and employ their body weight to maintain control.