The blue wall of silence came crumbling down on Friday in the murder trial of Derek Chauvin.

Minnesota’s longest-serving cop delivered damning testimony, saying his former colleague, Chauvin, used a level of force that was”totally unnecessary” and “uncalled for” in detaining George Floyd, the 46 year-old man killed in police custody last year (watch above).

“Pulling him down to the ground face down, and putting your knee on a neck for that amount of time is just uncalled for. I saw no reason why the officers felt they were in danger — if that’s what they felt — and that’s what they would have to feel to be able to use that kind of force,” said Lt. Richard Zimmerman, the head of the Minneapolis Police’s homicide unit.

Lt. Zimmerman, a 35 year veteran of the police department, said he’s taken training classes every year and has never been instructed to kneel on someone’s neck if they are prone. When a person is in handcuffs, Zimmerman explained “the threat level goes down all the way.” He added, “Once a person is in handcuffed, you need to get them out of the prone position as soon as possible because it restricts their breathing.”

On cross-examination, Chauvin’s lawyers tried to paint Zimmerman as too removed from street-level policing to understand the complicated dynamics that they say contributed to Floyd’s death. Defense lawyer Eric Nelson got Zimmerman to concede that police officers are allowed to improvise when they’re in dangerous situations.

But on redirect, a prosecutor asked Zimmerman if had seen “any need for Officer Chauvin to improvise by putting his knee on Mr. Floyd for nine minutes and 29 seconds.” Zimmerman responded, “No I did not.”

Zimmerman was the 19th witness called in the first week of the trial, which wrapped early on Friday. In the morning, jurors heard from the police officer who secured the crime scene following Floyd’s death.

The New York Times Timothy Arango reports:

Police testimony will continue today and into next week, underscoring one of the most unusual aspects of this case: so many officers testifying against one of their own. I’m told that many of them were more than willing to testify – no arm-twisting necessary from prosecutors – because they believe Derek Chauvin besmirched their profession.