Mr Chauvin's attorney Eric Nelson called a police use-of-force expert and a forensic pathologist to help make the case that Mr Chauvin acted reasonably against a struggling suspect and that Mr Floyd died because of an underlying heart condition and his illegal drug use.
Testifying could also give the jury the opportunity to see and hear any remorse or sympathy Chauvin might feel. Dr Martin Tobin noted hospital tests that showed Floyd's level was at most 2 per cent, within the normal range. He told reporters that they had not expected Mr Chauvin to testify, saying the prosecution "would have chopped him down second by second" on the time he knelt on Mr Floyd.
After closing arguments, the racially diverse jury will begin deliberating at the barbed-wire-ringed courthouse, with Minneapolis on edge against a repeat of the protests and violence that broke out last spring over Floyd's death. He would have been able to remove the mask he has had to wear at the defence table. It would have been Chauvin's first time publicly telling his side of the story.
However, the chief county medical examiner who ruled Floyd's death a homicide, Dr Andrew Baker, did not identify lack of oxygen, or asphyxia, as the cause of death.
They also called a forensic pathologist, former Maryland chief medical examiner Dr David Fowler, who said Floyd, whose death was ruled a homicide at the hands of the police, really died of heart disease, and that the exhaust fumes of the adjacent police vehicle may have also poisoned him.
Bystander video of Mr Floyd gasping that he couldn't breathe as bystanders yelled at Mr Chauvin to get off him triggered worldwide protests, violence and a furious examination of racism and policing in the US.
While the nine minutes and 29 seconds he knelt on Mr Floyd have been combed over by lawyers and experts, the man at the heart of the case has remained impassive and silent during almost three weeks of testimony with most of his face obscured by a face mask due to coronavirus restrictions.
Mr Floyd died past year in an incident in which he was handcuffed by police with the officer's knee pressed on his neck.