Officer Derek Chauvin had his knee on George Floyd's neck and was bearing down with most of his weight, the entire time the black man lay face-down with his hands cuffed behind his back, a use-of-force expert has testified.
Jody Stiger, a Los Angeles Police Department sergeant serving as a prosecution witness, told Chauvin's murder trial on Wednesday that based on his review of video evidence, Chauvin's knee was on Floyd's neck from the time officers put Floyd on the ground until paramedics arrived, about nine and half minutes, by prosecutors' reckoning.
Prosecutor Steve Schleicher showed jurors a composite image of five photos taken from various videos of the arrest.
Mr Stiger went through each photo, saying it appeared that the Minneapolis officer's left knee was on Floyd's neck or neck area in each one.
"That particular force did not change during the entire restraint period?" Mr Schleicher asked.
"Correct," Mr Stiger replied.
Mr Stiger also said Chauvin squeezed Floyd's fingers and pulled one of his wrists toward his handcuffs, a technique that uses pain to get someone to comply, but did not appear to let up while Floyd was restrained.
"Then at that point, it's just pain," Mr Stiger said.
Mr Stiger's testimony came a day after Chauvin's lawyer Eric Nelson sought to point out moments in the video footage when, he said, Chauvin's knee did not appear to be on Floyd's neck.
Mr Nelson also has suggested that bystanders who were yelling at Chauvin to get off Floyd distracted the officers, who perceived the onlookers as an increasingly hostile crowd.
On Tuesday, the defence lawyer got some police witnesses to acknowledge that jeering onlookers can make it more difficult for officers to do their duty.
But Mr Stiger told Mr Schleicher, "I did not perceive them as being a threat," even though some onlookers were name-calling and using foul language.
He added that most of the yelling was due to "their concern for Floyd".
It was Mr Stiger's second day on the stand.
On Tuesday, he testified that officers were justified in using force while Floyd was resisting their efforts to put him in a squad car.
But once Floyd was on the ground and stopped resisting, officers "should have slowed down or stopped their force as well".
Mr Stiger said that after reviewing video footage of the arrest, "my opinion was that the force was excessive".
Several experienced officers, including the police chief himself, have taken the stand as part of an effort by prosecutors to dismantle the argument that Chauvin was doing what he was trained to do when restrained Floyd last May.
According to testimony and records submitted on Tuesday, Chauvin took a 40-hour course in 2016 on how to recognise people in crisis, including those suffering from mental illness or the effects of drug use, and how to use de-escalation techniques to calm them down.
Records show Chauvin also underwent training in the use of force in 2018.
Johnny Mercil, a Minneapolis police use-of-force train, testified that those who attended were taught that the sanctity of life is a cornerstone of departmental policy and that officers must use the least amount of force required to get a suspect to comply.
Under cross-examination by Mr Nelson, Mr Mercil testified that officers are trained in some situations to use their knee across a suspect's back or shoulder and employ their body weight to maintain control.
"We tell officers to stay away from the neck when possible," But Mr Mercil added.
Mr Nelson has argued that the now-fired white officer "did exactly what he had been trained to do over his 19-year career" and he has suggested that the illegal drugs in Floyd's system and his underlying health conditions are what killed him, not Chauvin's knee.
Mr Nelson showed Mr Mercil several images taken from officers' body-camera videos, asking after each one whether it showed Chauvin's knee appearing to rest more on Floyd's back, shoulder or shoulder blades than directly on his neck.
Mr Mercil often agreed.
Chauvin, 45, is charged with murder and manslaughter in Floyd's death.
Floyd, 46, was arrested outside a neighbourhood market after being accused of trying to pass a counterfeit $US20 banknote.
