Chauvin, who is white, was fired by Minneapolis Police Department the day after he was captured on video last May with his knee on the neck of a handcuffed Floyd.
In body camera footage played on Wednesday, Chauvin could be heard defending his actions soon after to a bystander by saying Floyd was "a sizeable guy" who was "probably on something".
It was the first time the jury has clearly heard Chauvin speak.
He has pleaded not guilty to murder and manslaughter and a central dispute in the case is his lawyers' contention Floyd's death, which was ruled a homicide, was instead a drug overdose.
The jury watched video of a cheerful Floyd in his final minutes inside a grocery store, during which cashier Christopher Martin said his customer made friendly conversation and seemed under the influence of drugs.
Several other eyewitnesses spent the previous two days describing to the jury the shock of watching Floyd's struggle beneath Chauvin as bystanders screamed at police Floyd was falling unconscious.
Video footage of the arrest sparked global protests decrying police brutality against black people.
It was Martin's accepting of the $20 bill at Cup Foods grocery store that triggered everything that followed.
"I thought that George didn't really know it was a fake bill," the 19 year old told the jury.
He considered letting his employer dock it from his wages but ended up telling his manager and a few minutes later police were arresting Floyd on suspicion of passing a counterfeit.
Security video played for the jury shows Floyd approaching the counter, smiling, making cheerful conversation and putting his arm around a woman.
He appears filled with energy and constantly in motion, at one point almost dancing on the spot.
Martin said he made conversation with Floyd, asking him if he played baseball. Floyd seemed to take time to find his words but replied that he played football, Martin said.
"He seemed very friendly, approachable, he was talkative, he seemed to be having just an average Memorial Day, just living his life. But he did seem high."
Although a medical examiner ruled Floyd's death homicide resulting from the police restraint, fentanyl and methamphetamine was found in his blood and Chauvin's lawyers argue the death was really an overdose.
Martin sold Floyd cigarettes, after which his manager told him to go and confront Floyd, who had got back into a car outside.
Floyd was "just kind of shaking his head and putting his hands in the air, like, 'Why is this happening to me?'" Martin said.
Martin's manager told a co-worker to call police after Floyd refused to come back inside. Martin later said he was upset to see Chauvin on top of Floyd.
"They're not going to help us, this is what we deal with," he recalled telling another bystander.
Martin said he felt guilty.
"I thought if I would not have taken the bill this would have been avoided," he said.
One of the first to notice the arrest, Charles McMillan, 61, was in tears as he watched video of himself near Floyd as they dying man called out.
"You can't win!" McMillan can be heard telling Floyd over and over on the tape.
After Floyd's body was loaded into an ambulance, McMillan told Chauvin: "I don't respect what you did."
"I had to control this guy because he's a sizeable guy," Chauvin replies. "It looks like he's probably on something."