Looking Bad for the Killer.

An emergency room doctor who tried to save George Floyd’s life for 30 minutes before pronouncing him dead testified on Monday that he believed Mr. Floyd had most likely died of a lack of oxygen, bolstering a central argument of the prosecution.

Dr. Bradford T. Wankhede Langenfeld, who was a senior resident at the Hennepin County Medical Center, testified in court that Mr. Floyd’s heart was not beating by the time he arrived at the hospital on that day in May. His testimony followed those of two paramedics who said last week that Mr. Floyd’s heart had stopped by the time they arrived to the scene of his arrest. The doctor’s testimony came on the sixth day of the trial of Derek Chauvin, the former police officer charged with murdering Mr. Floyd.

The doctor said that, based on the information he had at the time, he thought that oxygen deficiency, sometimes called asphyxia, was “one of the more likely” causes of Mr. Floyd’s death.

Prosecutors had said Mr. Floyd died of asphyxia, appearing to divert from the ruling of the county medical examiner who performed an autopsy on Mr. Floyd and said that he had died of “cardiopulmonary arrest.” That term, prosecutors have said, is applicable to any death because it simply means that a person’s heart and lungs have stopped.

Eric J. Nelson, Mr. Chauvin’s lawyer, had suggested that Mr. Floyd’s death was caused in part by his underlying heart disease and the fentanyl and methamphetamine that were found in his system. In response to questions from Mr. Nelson, Dr. Wankhede Langenfeld agreed that many different things — including taking fentanyl and methamphetamine — could cause a death that would still be considered asphyxiation.