A paramedic testified on Thursday at the high-profile trial of the former Minneapolis police officer accused of killing George Floyd that the 46-year-old Black man was already dead when he arrived.

"When I showed up he was deceased and I dropped him off at the hospital and he was still in cardiac arrest," paramedic Derek Smith said on the fourth day of the murder and manslaughter trial of Derek Chauvin.

Chauvin, 45, was captured on video kneeling on the neck of a handcuffed Floyd for more than nine minutes during Floyd's May 25, 2020 arrest for passing a counterfeit $20 bill.

The video of Chauvin, who is white, restraining Floyd went viral and sparked protests against racial injustice and police brutality around the world. Prosecutors are seeking to prove that Chauvin's actions led to Floyd's death while the former officer's defence attorney has claimed that he died due to illegal drugs and underlying medical conditions.

Smith said Chauvin and other police officers were still on top of Floyd when he and his fellow paramedic Seth Bravinder arrived on the scene in an ambulance.

Smith said he checked the carotid artery in Floyd's neck to see if he had a pulse. "I did not feel one," he said. "In lay terms, I thought he was dead." Smith said he and Bravinder and the officers loaded Floyd into the ambulance and they tried to revive him using chest compressions and a defibrillator. Their efforts were unsuccessful.

"He's a human being and I was trying to give him a second chance at life," Smith said. Bravinder also told the court that when he and Smith arrived Floyd was "unresponsive." "I did not see him moving or breathing," he said. "He was limp."

Also testifying on Thursday was Courteney Ross, Floyd's girlfriend of nearly three years, and she was questioned extensively about Floyd's history of drug use. Ross, a 45-year-old mother of two who works in a coffee shop, said she had been Floyd's girlfriend since August 2017. She cried as she recounted their first meeting, which took place at a homeless shelter where Floyd had been working as a security guard.