MINNEAPOLIS — One of the most important witnesses in the murder trial of former Minneapolis police officer Derek Chauvin is expected to take the stand Friday, prosecutors said, capping off a long week of highly technical legal and medical testimony.

Last year, Dr. Andrew Baker, the Hennepin County chief medical examiner, ruled George Floyd’s death a homicide. He said Floyd’s heart and lungs stopped amid “law enforcement subdual, restraint and neck compression.”

Friday morning, a former county medical examiner who trained Baker said Floyd died from low oxygen. “This is a death where both heart and lungs stop working. The point is it’s due to law enforcement subdual restraint and compression,” said Dr. Lindsey Thomas.

Baker’s testimony will be key to prosecutors, who say Floyd was killed by Chauvin’s knee on his neck for more than nine minutes. The defense argues Floyd died as a result of the drugs in his system and underlying medical issues.

Chauvin is charged with second-degree murder, third-degree murder and second-degree manslaughter in Floyd’s death.

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Latest updates:

  • Forensic pathologist Dr. Lindsey Thomas, who trained Baker and reviewed documents in the case, took the witness stand Friday morning.
  • Jurors have heard from 34 witnesses so far – all called by the prosecution.
  • A medical expert in the physiology of breathing said Thursday the way Floyd was restrained prevented him from breathing properly and caused his death.
  • Another, a police surgeon, said Floyd didn’t overdose or have a heart attack.
  • A forensic toxicologist who analyzed George Floyd’s blood and urine told jurors Thursday the amount of meth in Floyd’s system was consistent with a prescribed dose – a “very low” amount.

Forensic pathologist: George Floyd died from asphyxia, or low oxygen

Friday morning, the prosecution called forensic pathologist Dr. Lindsey Thomas to the stand as an expert witness who has reviewed documents and videos in the case. She also trained Dr. Andrew Baker, the Hennepin County chief medical examiner who ruled Floyd’s death a homicide.

Thomas said she agreed with Baker’s autopsy. “In this case, I believe the primary mechanism of death is asphyxia, or low oxygen,” she said. “This is not a sudden cardiac death. It’s a death where both the heart and lungs stopped working.”

Baker did not use the word “asphyxia” in his autopsy, but the federal Armed Forces Medical Examiner System, which reviewed that autopsy, said the “subdual and restraint had elements of positional and mechanical asphyxiation. A family-commissioned autopsy released around the same time found Floyd’s death was a homicide caused by “asphyxiation from sustained pressure.”

Thomas retired in 2017 but still does consulting work. Previously, she was the medical examiner for several Minnesota counties. She said she’s performed about 5,000 autopsies and has consulted with other medical examiners on roughly 1,000 more autopsies.

Thomas said the physical examination of the body is only “a tiny part” of the investigation, which involves examining the deceased person’s medical record, what they were doing before death, plus the autopsy.

“In this case, the autopsy didn’t tell me the cause and manner of death,” Thomas said, so she also examined the videos of the police struggle with Floyd and other evidence.

“Basically, Mr. Floyd was in a position … where he was unable to get enough oxygen,” Thomas said. Her testimony confirmed prior testimony by Dr. Martin Tobin and Dr. Bill Smock, other expert witnesses called by the prosecution.

Thomas said the autopsy was “really great for ruling things out.” She said there was no evidence from the autopsy that Floyd had sufficient lung disease to impair his breathing. He didn’t have a heart attack or a stroke, she said. And the slow nature of Floyd’s death shows he did not die of a methamphetamine or fentanyl overdose, she said.

“Over time you can see that his breathing is getting more and more difficult, and his breathing is getting less and less,” Thomas said. Minutes later, there’s an anoxic seizure, which she described as “part of a twitch,” that signaled his brain wasn’t getting enough oxygen. But the police restraints continued for minutes afterward, Thomas said.

Doctor testifying for prosecution says ‘what Mr. Floyd was subjected to’ would kill a healthy person

Dr. Martin Tobin, a physician who has been working in respiratory physiology for 40 years, testified Thursday that Floyd died from a “low level of oxygen,” which caused damage to his brain and an abnormal heartbeat. Tobin was called as an expert witness by prosecutors and examined records and video in the Floyd case, but he did not conduct an examination of Floyd’s body.

In this image from video, Dr. Martin Tobin testifies as Hennepin County Judge Peter Cahill presides Thursday, April 8, 2021, in the trial of former Minneapolis police Officer Derek Chauvin at the Hennepin County Courthouse in Minneapolis, Minn. (Photo: AP)

Tobin said he watched videos of Floyd’s arrests “hundreds of times” and found Chauvin’s left knee was on Floyd’s neck for the majority of the time. The combination of Floyd being handcuffed behind his back, the officers’ manipulation of the cuffs, and the pavement beneath Floyd combined to interfere with Floyd’s ability to breathe, Tobin testified.

The overall effect of the restraint was almost “as if a surgeon had gone in and removed the lung,” he said, referring to Floyd’s left lung. “A healthy person subjected to what Mr. Floyd was subjected to would have died as a result of what he was subjected to,” Tobin said. Read more about his testimony here.

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