Derek Chauvin’s police supervisor has told his murder trial that there was no justification for the officer to keep his knee on George Floyd’s neck for nine minutes. Sgt David Pleoger, who arrived at the scene shortly after Floyd was taken away by ambulance, said that Chauvin and other officers holding down the 46-year-old Black man should have stopped using force once Floyd stopped resisting. “When Mr Floyd was no longer offering up any resistance to the officers they could have ended their restraint,” he said. Video recording showed that Chauvin kept pressing his knee into Floyd’s neck even after the detained man pleaded that he could not breathe and then stopped moving. Two other officers were also holding Floyd down. Chauvin, 45, who is white, has denied charges of second- and third-degree murder, and manslaughter, over Floyd’s death. He faces up to 40 years in prison if convicted of the most serious charge. Pleoger is among a number of officers expected to be called as witnesses for the prosecution including the chief of the Minneapolis police department, Medaria Arradondo, who, in a highly unusual move, will give evidence against his own former officer. Arradondo fired Chauvin shortly after Floyd’s death. Pleoger was alerted to concerns about the arrest by a 911 emergency operator and called Chauvin on his cellphone. In the conversation, Chauvin can be heard saying: “We just had to hold a guy down. He was going crazy.” The supervisor then headed to the scene to determine whether an appropriate level of force has been used. Pleoger said that the first he became aware that Chauvin had his knee on Floyd’s neck was when one of the other officers suggested he ask Chauvin about it. Even then, he said, Chauvin did not reveal its full extent. Pleoger said all police officers are trained that if a suspect is restrained with handcuffs on the ground, they should be turned on to their side as soon as possible because of the danger of “positional asphyxia”. “If they are left on chest or stomachs for too long, their breathing can be compromised,” he said. Floyd was kept in a prone position throughout despite his evident difficulty breathing. Earlier on Thursday, Floyd’s girlfriend told the trial that the couple shared an addiction to opioid painkillers that they struggled to overcome in the weeks before his death. Courteney Ross said that Floyd had been clean for a while after she took him to hospital when he overdosed, but that he started using again about two weeks before his arrest by Chauvin, a former Minneapolis police officer, last May. The bulk of Ross’s often tearful testimony on the fourth day of the trial focused on the pair’s opioid use, as the prosecution sought to head off defense claims that Floyd was killed by drugs because he had opioids and methamphetamine in his system. Ross’s account helps establish that Floyd built up a tolerance to opioids, and that the relatively small amount recorded in the official autopsy would not have been enough to kill him. The prosecution is also seeking to undermine defense claims that the level of force used by Chauvin in kneeling on Floyd’s neck for about nine minutes was justified because the detained man was high on drugs. Ross, who dated Floyd for about three years, said they both became hooked after being prescribed opioids to treat chronic pain. “We got addicted and we both tried to break that addiction many times,” she said. Ross said sports injuries led to Floyd’s addiction to prescription pills obtained legally before the pair started buying black market drugs, including from Maurice Hall, the man who was in the car with Floyd at the time of his death. These included oxycodone pills, including the powerful prescription opioid OxyContin. Chauvin’s defense has claimed Floyd was overdosing at the time and that it contributed to his death from heart failure. The state medical examiner’s report on Floyd’s death recorded that he had the powerful opioid fentanyl and methamphetamine in his system when he died, but it did not list them as a cause of his death. On Thursday, Derek Smith, the first paramedic on the scene, said that when he arrived he saw three police officers on top of Floyd but no one giving medical treatment. “He wasn’t moving. I didn’t see any chest rise or fall,” he said. The paramedic tried to find a pulse in Floyd’s neck but could not find one. The trial continues.