Department use-of-force instructor Lt. Johnny Mercil became the latest member of the Minneapolis force to take the stand 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 on May 25, 2020.
Mercil is a key witness because he’s the first use-of-force expert the jurors have heard from, and he carries additional credibility because he is specifically familiar with and teaches Minneapolis Police Department use-of-force policies.

Derek Chauvin, a police officer who was later fired, was one of four to respond to a 911 call concerning counterfeit money allegedly being used at a convenience store in Minneapolis last year.

George Floyd, who was accused of using the money, resisted officers’ attempts to put him into the back of a patrol car. They then pinned him to the ground. Chauvin knelt on his neck for close to 9 1/2 minutes by prosecutors’ reckoning to keep him in place.
Floyd, 46, experienced cardiopulmonary arrest while being restrained by officers, according to the Hennepin County Medical Examiner’s Office, which determined the manner of death was homicide.
He had high levels of fentanyl and methamphetamine in his system, according to substance screening, and that drug use possibly contributed to the death, along with a history of heart disease.
According to testimony and records submitted Tuesday, Chauvin took a 40-hour course in 2018 on how to recognize people in crisis—including those suffering mental problems or the effects of drug use—and how to use de-escalation techniques to calm them down.
Eric Nelson, the attorney for Chauvin, has maintained that Chauvin “did exactly what he had been trained to do over his 19-year career,” in the May 2020 incident.

He has offered that Floyd’s history of heart disease, along with the high levels of fentanyl and methamphetamine in his system are what caused his death, not Chauvin’s restraining methods.
When showed images from officer body-worn camera footage of moments during Floyd’s arrest, Mercil, who is is currently on medical leave from the police department, told Nelson that it showed Chauvin using a “prone hold an officer may apply with his knee.”

Mercil, when questioned about whether he had trained department officers that if an individual is able to talk while in the prone position then they can also breathe, he responded: “Yes, it’s been said.”
He testified that Chauvin’s shin appeared to be placed directly along Floyd’s neck in at least one of the images. He often agreed with Nelson however that Chauvin appeared to place his knee more on Floyd’s back, shoulder or shoulder blades, more so than on Floyd’s neck.

Mercil said using a knee on the neck or back can be an authorized use of force, but it’s usually transitory and depends on the time frame and type of resistance. If the subject is handcuffed and not resisting, it is not authorized, Mercil said. Once the subject is handcuffed and compliant or not resisting, then it’s “an appropriate time” for the officer to move their knee, Mercil said, adding: “We tell officers to stay away from the neck when possible.”
“There’s the possibility and risk that some people have trouble breathing when they’re handcuffed (to their back) and on their stomach,” Mercil said. A person is rolled on their side to prevent positional asphyxia, Mercil said. The officer should turn the person to this position “sooner the better,” though he noted it depends on the situation and environment.


Officers should change their force if the force they’re facing changes to the situation upon reassessment, Mercil said.
Sanctity of life and the protection of the public is a cornerstone of the department’s use of force policy, Mercil said. Use of force includes applying a restraint, which must be reasonable, per the U.S. Constitution’s Fourth Amendment, and a 1989 Supreme Court case.

Floyd repeatedly told Chauvin that “I can’t breathe” when he was pinned down.
Chauvin has pleaded not guilty to second-degree murder, second-degree manslaughter, and third-degree murder charges.