Mr Floyd's treatment by police was captured on widely seen bystander video, that sparked protests around the U.S. as people demonstrated against racial inequality.
The friend, Morries Hall, was in the auto with Floyd when police arrived, setting the stage for the attempt to arrest Floyd. Chauvin's lawyers argue that Floyd's death was really a drug overdose.
No witnesses at the scene were arrested, and several of them have testified that they urged officers to check Mr Floyd's pulse and provide him with medical care.
Mr Nelson, Chauvin's attorney, noted on cross-examination that department policies direct officers to do what is reasonable in a given situation.
Kneeling on people's necks is not what officers are taught, Derek Chauvin's former boss told the jury. He said officers are trained to put their knee across a suspect's back or shoulders and use their weight to restrain them, but we "tell officers to stay away from the neck when possible".
He said that Mr Floyd had no ability to resist or show aggression once he was face down on the ground.
The court heard that Derek Chauvin, accused of killing Floyd, completed 40 hours of intervention training.
Earlier Monday, the emergency room doctor who pronounced Floyd dead after trying to resuscitate him testified that he theorized at the time that Floyd's heart most likely stopped because he didn't get enough oxygen.
Mr Chauvin's defence team has contended that alleged drug use and an underlying heart condition contributed to Mr Floyd's death.
Sgt Jody Stiger, a use of force expert for the Los Angeles Police Department, testified that officers were initially justified in their actions because Mr Floyd was "actively resisting" arrest as he was being placed in the patrol auto.
He also said officers were taught that restraint is considered force and that they must use the least force required because "it's safer and better for everybody involved".
Arradondo testified that Chauvin, a 19-year veteran of the force, should have let Floyd up sooner and that the pressure on Floyd's neck did not appear to be light to moderate, as called for under the department's neck-restraint policy. Prosecutors said Chauvin continued to kneel on Floyd's neck for 9 minutes, 29 seconds, after he was handcuffed behind his back and lying on his stomach, even though Floyd said 27 times that he could not breathe.
Arradondo, the city's first Black chief, fired Chauvin and three other officers the day after Floyd's death.
Mr Nelson has suggested that onlookers, many of whom were shouting at Chauvin, might have affected officers' response.
Chauvin's lawyer Eric Nelson confirmed he wanted to ask if Hall sold or gave Floyd drugs. Experts have shared with Law Officer that there are two distinct possibilities for this.
Before testimony began, lawyers argued over whether a man who was with Mr Floyd at Cup Foods on the day of his death should be forced to speak during the trial.
Morries Hall, who was with Floyd in his auto shortly before his death, is in custody and appeared by video camera at the hearing after he was subpoenaed to testify.
The judge said he would push the decision until next week, and asked Mr Chauvin's defence lawyer to prepare a list of possible questions for Mr Hall.