

MINNEAPOLIS — The police officer had seen hundreds of crime scenes, interviewed scores of witnesses and made his share of arrests over more than 35 years working cases in Minneapolis.
But when Lt. Richard Zimmerman watched a video of one of his colleagues kneeling on George Floyd’s neck, he saw what he described in a courtroom on Friday as a “totally unnecessary” violation of department policy.
“Pulling him down to the ground facedown and putting your knee on a neck for that amount of time, it’s just uncalled-for,” testified Lieutenant Zimmerman, who is the longest-serving officer on the Minneapolis police force. His comments came at the end of the first week in the trial of Derek Chauvin, the former police officer charged with murdering Mr. Floyd along a Minneapolis street last May.
Police officers have often been accused of sticking together on questions of misconduct — avoiding breaking a so-called blue wall of silence — so the sworn testimony against Mr. Chauvin by a high-ranking officer was all the more extraordinary.
the 12 jurors who are expected to decide the verdict.
“If you’re kneeling on a person’s neck, that can kill him,” said Lieutenant Zimmerman, who has led the Minneapolis department’s homicide unit since 2008. Officers are supposed to turn people onto their sides or sit them up once they are restrained, he said, because leaving them in prone positions can make it hard to breathe.
Mr. Chauvin and two other police officers had continued to pin Mr. Floyd, who was handcuffed, against the ground after he was no longer responsive. That decision, Lieutenant Zimmerman suggested, meant the officers had violated their duty to take care of someone in their custody.
teenager who filmed the widely viewed video of Mr. Chauvin kneeling on Mr. Floyd for more than nine minutes, the convenience store clerk who told his manager that Mr. Floyd had paid for cigarettes using a fake $20 bill, and Mr. Floyd’s girlfriend, who described their shared struggle with opioid addiction.
The testimony from police officials, though, marked a shift to a different phase of the case: Prosecutors have said they will show that Mr. Chauvin’s actions were unusually brutal — and amounted to a crime.
In cross-examining Lieutenant Zimmerman, Eric J. Nelson, the lawyer for Mr. Chauvin, suggested that the lieutenant’s experience on the streets might be dated. Lieutenant Zimmerman had not regularly patrolled the streets as a uniformed officer since 1993, Mr. Nelson noted, offering that he might no longer be familiar with the force needed. At one point, Mr. Nelson asked Lieutenant Zimmerman when he had last gotten into a fight with someone while on duty; 2018, the lieutenant answered.
Under questioning, Lieutenant Zimmerman acknowledged that people sometimes become more combative when revived after a period of unconsciousness and said that police officers had been trained to kneel on people’s shoulders, in some circumstances, while handcuffing them.
He said that once people are handcuffed, they usually present only a minor threat, though they can still be combative and try to hurt officers, such as by kicking them.
“Once a person is cuffed, the threat level goes down all the way,” Lieutenant Zimmerman said. “They’re cuffed; how can they really hurt you?”