UPDATE: April 15, 12:30 p.m. ET ― In a tense morning of pretrial business in Judge Peter Cahill’s courtroom Thursday, prosecutors revealed that Dr. Andrew Baker, the Hennepin County medical examiner who performed George Floyd’s autopsy, had unearthed a record of the gases present in Floyd’s blood.

Jerry Blackwell, an attorney for the prosecution, said that Baker had reached out to his team following the Wednesday testimony of Dr. David Fowler. The results showed that Floyd did not have an abnormal level of carbon monoxide in his blood ― contrary to Fowler’s suggestion that Floyd’s position near the back end of a police vehicle may have exposed him to harmful exhaust fumes.

Cahill chastised the prosecution for not digging deeper to find the records when they first found out that Fowler was going to bring up carbon monoxide in his testimony, and upon threat of mistrial prohibited the prosecution from referring to the new evidence before the jury.

The judge’s direction meant that Blackwell had to keep Dr. Martin Tobin ― the pulmonologist previously called by prosecutors who testified about the way Floyd died ― on a very tight leash when he recalled him to the stand to rebuff some of Fowler’s statements. But Tobin managed to address the carbon monoxide issue in a roundabout way, referring to blood oxygen records that were already part of evidence to explain to the jury that the oxygen left no room for an elevated carbon monoxide level in Floyd’s system.

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A medical expert called by former Minneapolis police officer Derek Chauvin’s defense spoke at length Wednesday about the possibility that carbon monoxide poisoning could have played a role in George Floyd’s death last spring while in police custody.

Yet the expert, Dr. David Fowler, former chief medical examiner for the state of Maryland, also acknowledged that it did not appear anyone ever measured Floyd’s blood for carbon monoxide.

“I could not find a reference to it, no,” Fowler testified in court.

His testimony also raises the question of who was responsible for keeping Floyd pinned down with his head near the tailpipe of a police vehicle, therefore potentially exposing him to the poisonous gas.

On cross-examination, prosecutor Jerry Blackwell tried to show how Fowler’s assessment amounted to pure speculation, as he did not have measurements on Floyd’s blood or know definitively whether the car had been on.

Floyd died on May 25, 2020, after being cuffed with his hands behind his back and pinned to the pavement for more than nine minutes by Chauvin and other officers.

Defense attorney Eric Nelson called Fowler to the stand on Wednesday to discuss alternative explanations for Floyd’s death other than what was written on his death certificate ― “cardiopulmonary arrest complicating law enforcement subdual, restraint and neck compression.” Instead, Fowler testified, he would have said Floyd died of “cardiac arrhythmia due to hypertensive atherosclerotic cardiovascular disease during the restraint.”

Instead of “homicide,” Fowler would have classified Floyd’s manner of death under “undetermined.” (The Centers for Disease Control and Prevention requires death certificates to list one of five manners of death, primarily for data collection purposes.)

Effectively, Fowler would have shifted blame from law enforcement officers’ actions to Floyd’s preexisting health conditions, which included heart disease.

In his capacity as Maryland’s former top medical examiner, Fowler is currently being sued by the family of Anton Black, an unarmed 19-year-old Black man who died in police custody in 2018 after a chase that ended in front of his mother’s house. The teen’s sister told local news station WTOP that she considered her brother’s death and Floyd’s death to be eerily similar.

At Chauvin’s trial, Fowler testified that even though cars manufactured recently come with equipment that “dramatically” reduces the amount of carbon monoxide they emit, people with heart disease are more sensitive to car exhaust.

“It has the potential to affect individuals at a much lower level than you would find with healthy individuals,” Fowler said.

His testimony comes during the third week of the trial. Prosecutors called several medical experts of their own over the course of the first two weeks ― including the doctor who wrote Floyd’s death certificate and a renowned pulmonologist who said he could calculate the precise moment Floyd ran out of air in his lungs and died.

So far, the defense has called one other expert witness: Barry Brodd, a former police officer and consultant on use of force. Brodd was forced to walk back some of his testimony about the officers’ actions during cross-examination on Tuesday.