Former Minneapolis police officer Derek Chauvin held his knee against 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 testified Wednesday.

Chauvin, 45, is standing trial on murder and manslaughter charges in connection with Floyd’s May 2020 death. Prosecutors allege that Chauvin held his knee on Floyd’s neck for 9 minutes and 29 seconds, despite Floyd being handcuffed, in the prone position. Floyd was later declared dead.

Police were responding at the time to a report that Floyd, 46, had tried to use a counterfeit $20 bill while buying cigarettes at a neighborhood convenience store, Cup Foods. Chauvin and three other officers were fired after Floyd's death. 

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On Wednesday, Los Angeles Police Department Sgt. Jody Stiger testified as an expert witness on behalf of the prosecution. Stiger said 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.  

"That particular force did not change during the entire restraint period?" prosecutor Steve Schleicher asked as he showed the jury a composite image of five photos taken from the various videos of the arrest.

"Correct," Stiger replied.

Stiger’s testimony came a day after Chauvin attorney 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.

Bystander video of Floyd crying that he couldn’t breathe as onlookers yelled at Chauvin to get off him sparked protests and scattered violence across the U.S. and triggered a reckoning over racism and police brutality.

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.

Nelson seized on the drug angle in cross-examining Stiger, playing a snippet of then-Officer J. Kueng's bodycam video and asking whether Stiger could hear Floyd say, "I ate too many drugs."

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Stiger replied that he could not make out those words in the footage. Prosecutors did not bring up the issue when they questioned Stiger again.

Nelson has also contended that the officers on the scene perceived the onlookers as an increasingly hostile crowd and were distracted by them. On Tuesday, the defense attorney got some police witnesses to acknowledge that jeering bystanders can make it more difficult for officers to do their duty.

On Wednesday, Stiger told the jury, "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 Mr. Floyd."

"I would describe a hostile crowd as a crowd or members of the crowd that were threatening and throwing bottles and rocks at police," he said.

Nelson’s voice rose as he asked Stiger how a reasonable officer would be trained to view a crowd while dealing with a suspect, "and somebody else is now pacing around and watching you and watching you and calling you names and saying (expletives)." Nelson said "this could be viewed by a reasonable officer as a threat."

In this image from video, defense attorney Eric Nelson, left, and defendant, former Minneapolis police Officer Derek Chauvin, right, listen as Hennepin County Judge Peter Cahill presides in the trial of Chauvin, Tuesday, April 6, 2021, at the Hennepin County Courthouse in Minneapolis. Chauvin is charged in the May 25, 2020, death of George Floyd. (Court TV via AP, Pool)

"As a potential threat, correct," Stiger said.

The defense attorney also asked Stiger whether the video showed Floyd pick up his head and move it at times.

"Slightly, yes. He attempted to," Stiger replied.

In his cross-examination, Chauvin's lawyer also noted that dispatchers had described Floyd as between 6 feet and 6-foot-6 and possibly under the influence. Stiger agreed it was reasonable for Chauvin to come to the scene with a heightened sense of awareness.

Stiger further agreed with Nelson that an officer’s actions must be viewed from the point of view of a reasonable officer on the scene, not in hindsight.

The defense attorney suggested that when Chauvin told Floyd to "relax," he was trying to calm him down and reassure him. And Nelson said that given typical EMS response times, it was reasonable for Chauvin to believe that paramedics would be there soon.

In this image from video, witness Jody Stiger, a Los Angeles Police Department sergeant testifies as Hennepin County Judge Peter Cahill presides Wednesday, April 7, 2021, in the trial of former Minneapolis police Officer Derek Chauvin at the Hennepin County Courthouse in Minneapolis. (Court TV via AP, Pool)

Stiger also testified that Chauvin squeezed Floyd’s fingers and pulled one of his wrists toward his handcuffs. He said that it appeared Chauvin utilized the practice of "pain compliance," which is a technique used to cause pain and, in the process, get a person to comply. When asked if he believed Floyd was trying to resist arrest, Stiger said, "No."

But if someone does not have the chance to comply, "then at that point it's just pain," Stiger said.

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Stiger said Chauvin did not appear to let up while Floyd was restrained.

"At the time of the restraint period, Mr. Floyd was not resisting – he was in the prone position, he was handcuffed," Stiger said. "He was not attempting to evade, he was not attempting to resist, and the pressure that was being caused by the body weight could cause positional asphyxia, which could cause death."

Asked by prosecutors whether Chauvin had an obligation to take Floyd’s distress into account as he was considering what level of force to use, Stiger replied: "Absolutely. As the time went on, clearly in the video, you could see that Mr. Floyd’s ... health was deteriorating. His breath was getting lower. His tone of voice was getting lower. His movements were starting to cease."

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"So at that point, as a [sic] officer on scene, you have a responsibility to realize that, ‘OK, something is not right, something has changed drastically from what was occurring earlier,'" Stiger continued. "So therefore you have a responsibility to take some type of action."

It was Stiger's second day on the stand. On Tuesday, he testified that the force used against Floyd was excessive. He said police 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."

Fox News’ Danielle Wallace contributed to this report, as well as the Associated Press.