Dr. Andrew Baker, the Hennepin County medical examiner, testified Friday in a Minneapolis courtroom as prosecutors try to prove former Minneapolis police officer Derek Chauvin was responsible for George Floyd's death in police custody last May.
Prosecutor Jerry Blackwell questioned Baker about the autopsy report he had completed in Floyd's death, which cites "cardiopulmonary arrest complicating law enforcement subdual, restraint, and neck compression."
Baker concluded that Floyd's death was a homicide — which as a forensic pathologist he explained means that someone else was involved in the death, not necessarily that it was criminal.
Blackwell asked how it was the subdual, restraint and neck compression caused Floyd's death.
Baker explained that Floyd had severe underlying heart disease. Floyd also had hypertensive heart disease, Baker said, "which means that his heart weighed more than it should."
"So he has a heart that already needs more oxygen than a normal heart, by virtue of its size. And it's limited in its ability to step up to provide more oxygen when there's demand, because of the narrowing of his coronary arteries," Baker said.
"Now in the context of an altercation with other people that involves things like physical restraint, that involves things like being held to the ground, that involves things like the pain you would incur from having your cheek up against the asphalt, an abrasion on your shoulder – those events are going to cause stress hormones to pour out into your body, specifically things like adrenaline," Baker continued. "And what that adrenaline is going to do is it's going to ask your heart to beat faster. It's going to ask your body for more oxygen so that you can get through that altercation."
"In my opinion, the law enforcement subdual, restraint and the neck compression was just more than Mr. Floyd could take, by virtue of those heart conditions," Baker concluded.
There were fentanyl and methamphetamine in Floyd's toxicology report, Blackwell noted, and inquired why Baker had not listed those as the "top line" causes of death in his report.
"The top line of the cause of death is really what you think is the most important thing that you think precipitated the death. Other things that you think played a role in the death but were not direct causes" appear in the "other significant conditions" part of the death certificate, Baker explained.
"Mr. Floyd's use of fentanyl did not cause the subdual or neck restraint, his heart disease did not cause the subdual or the neck restraint," Baker said. They were items that may have contributed to his death but were not the direct cause, he said.
During cross-examination, defense attorney Eric Nelson asked Baker whether Floyd's heart disease, history of hypertension and the drugs in his system played a role in his death.
"In my opinion, yes," Baker replied.
Nelson asked Baker about the effects of methamphetamine in the circumstances of this case: A person with an enlarged heart and a narrowing of the arteries, how does the introduction of methamphetamine affect that person?
"It increases the heart rate, it increases the work of the heart. It's not something that I as a forensic pathologist would want to see in the blood of someone that has heart disease," Baker replied.
Blackwell, for the prosecution, asked Baker what he believes were the cause and manner of death, and Baker said that his opinion has not changed from his earlier determinations.
Before the Hennepin County medical examiner, the court heard from forensic pathologist Dr. Lindsey Thomas. She appeared as an expert for the prosecution, but she said she was not being paid to testify.
"I've never had a case like this," she said, where a person's death is so thoroughly documented – mainly through videos from the scene.
When asked if she formed an opinion on "the mechanism" of Floyd's death, Thomas said she has.
"In this case, I believe the primary mechanism of death is asphyxia or low oxygen," she told the jury.
The Hennepin County medical examiner's office ruled last summer that Floyd's death was a homicide, saying his heart and lungs stopped functioning "while being restrained" by police. But it also noted "other significant conditions," including fentanyl intoxication and recent methamphetamine use as well as heart disease.
Chauvin's attorney, Nelson, has said Floyd's heart condition was also to blame for his death. Nelson has also said Floyd may have been overdosing on drugs when he died, airing the theory that Floyd put drugs in his mouth when police approached him.
Under questioning from Nelson, Thomas said she would consider Floyd's heart to be "slightly enlarged," but she added that by some measures, his heart would not be considered to be enlarged.
High blood pressure is the primary cause of an enlarged heart, Thomas said. She also confirmed that Floyd had a history of high blood pressure.
On Thursday, pulmonary specialist Dr. Martin Tobin told the jury that Floyd died from a lack of oxygen that caused brain damage after the first five minutes of the police officers' restraint of him.
Tobin also said that fentanyl did not play a role, citing Floyd's normal breathing rate. It would have been much slower, he said, if Floyd was under the effects of fentanyl.
Thomas worked for years in the Hennepin County medical examiner's office, and also worked for or led similar agencies in Minnesota. She's now semiretired, she said, but works part time in medical examiner's offices in Reno, Nev., and Salt Lake City. She is licensed in several states and has performed thousands of autopsies. She and Baker are friends and former colleagues, she said.
Chauvin is charged with three criminal counts: second-degree murder — unintentional — while committing a felony; third-degree murder — perpetrating eminently dangerous act and evincing depraved mind; and second-degree manslaughter — culpable negligence creating unreasonable risk.