Multiple medical examiners took the stand in Derek Chauvin's murder trial on Friday, testifying that George Floyd died from a lack of oxygen. 

Chauvin's lawyers have repeatedly tried to suggest that Floyd was killed by drugs in his system and heart issues, the New York Times reported.

But on Friday, Dr. Lindsey Thomas, a former Hennepin County Medical Examiner who retired in 2017, told the court that it was the knee on his neck that killed him, the Minneapolis Star-Tribune reported. She spent 37 years as a medical examiner and now works as a forensic pathologist in Reno and Salt Lake City.

"In this case, I believe the primary mechanism of death is asphyxia or low oxygen," Thomas said.

"The activities of the law enforcement officers resulted in Mr. Floyd's death and specifically those activities were the subdual restraint and the neck compression. What I observed from all of these videos is this was not a sudden death. It's not like snow shoveling when someone clutches their chest and falls over. There was nothing sudden about his death," she added. 

"There's no evidence to suggest [George Floyd] would have died that night except for the interactions with law enforcement," Thomas testified.

She went on to explain that even though his heart stopped, that does not mean he died from a heart attack. 

She also shot down attempts by Chauvin's lawyers to say that Floyd died of a drug overdose, telling the court that the methamphetamines and fentanyl did not contribute to his death. 

Other experts, like Dr. Martin Tobin, said that Chauvin's knee, which was on Floyd's neck for more than nine minutes, deprived his body of oxygen and "caused damage to his brain that we see, and it also caused a [pulseless electrical activity] arrhythmia that caused his heart to stop."

Tobin is an expert on lungs and according to the Minneapolis Star-Tribune, has spent decades specializing in respiratory and critical care medicine. 

Hennepin County Medical Examiner Dr. Andrew Baker is expected to testify on Friday as well, and will be a key witness for both sides.

Baker caused outrage in June 2020 when he released his report on Floyd's death, identifying heart problems, the drugs in his system and the choking by Chauvin as possible causes of death. Despite his findings, he still ruled Floyd's death a homicide, citing the "cardiopulmonary arrest complicating law enforcement subdual, restraint, and neck compression" as the main reason for Floyd's death. 

Tobin said Floyd's health conditions had nothing to do with his death. 

Another medical expert, Louisville Police Department police surgeon Dr. Bill Smock, explained what it looks like when someone dies from an overdose of fentanyl and said Floyd's death did not resemble that. 

"He's breathing, he's talking, he's not snoring, he is saying, 'Please, please, get off me, I want to breathe, I can't breathe.' That is not a fentanyl overdose, that is someone begging to breathe," Smock said.  

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