Dr Bradford Wankhede Langenfeld, the emergency room doctor at the Hennepin County Medical Centre who cared for George Floyd the day he died, testified at the trial of Derek Chauvin on Monday, saying the lack of oxygen was likely the cause of his death.

"I felt that the high CO2 may have suggested a respiratory cause," Langenfeld answered to the Defence attorney Eric Nelson after acknowledging Floyd's unusual high levels of CO2 after tests had been taken.

Langenfeld also acknowledged the low likelihood of Floyd having had a heart attack, as the patient had not registered chest pain or chest clutching, along with the fact that he was in a PEA state (pulseless electrical activity), after prosecutor Jerry Blackwell asked whether Floyd's cardiac arrest was likely the result of a heart attack.

The physician also noted that he had not discarded 'excited delirium,' a diagnosis sometimes cited in cases where civilians die at the hands of the police, which he would later disregard as the patient was not presenting the associated symptoms, including sweating or an agitated state.

Derek Chauvin has been charged with second-degree murder and manslaughter and third-degree murder after being filmed kneeling on George Floyd's neck for nearly nine minutes before he was pronounced dead.