An expert witness delivered a devastating blow to Derek Chauvin’s defense strategy, telling jurors that a “low level of oxygen” caused George Floyd to die (watch above). Chauvin, a former Minnesota police officer, knelt on Floyd’s neck for over nine minutes, but his lawyers have suggested that Floyd died because of drugs found in his system.

Dr. Martin Tobin, a pulmonologist and national breathing expert, undercut that theory, saying “a healthy person subjected to what Mr. Floyd was subjected to, would have died.” He added that video shows Floyd had a normal respiratory rate before he was restrained, indicating that fentanyl – the powerful opioid Floyd was addicted to – didn’t have an impact on his breathing. “Basically it’s telling you fentanyl is not on board, it is not having an effect on his respiratory centers,” Dr. Tobin said.

Dr. Tobin, who was not paid for his testimony, said Floyd’s leg movements indicated that he was having a seizure while Chauvin pinned him down. He noted that Chauvin kept his knee on Floyd’s neck even after Floyd ran out of oxygen. “The knee remained on the neck for another 3 minutes and 2 seconds, after we reached the point where there was not one ounce of oxygen left in the body,” Dr. Tobin testified, noting that he had carefully examined the relevant video evidence and medical records.

Dr. Tobin underscored the effort Floyd made under Chauvin’s knee to fight for oxygen. He said Floyd was essentially in a “vise” – restrained by handcuffs, the concrete ground, and the weight of police officers. “Keep in mind the left side is nonfunctional from the way they have manipulated him and pushed him into the street so he’s constantly, cranking up his right side of his body…He’s making repeated struggling movements,” he said.

Highlighting a specific moment in the body cam footage of Floyd’s death, Dr. Tobin told jurors that Floyd’s squirming fingers indicate that he’s fighting for his life. “To most people, this doesn’t look terribly significant. But to a physiologist, this is extraordinarily significant. This tells you that he has used up his resources and he’s now literally trying to breathe with his fingers and knuckles,” he testified.

Prosecutors asked Tobin about the phrase ‘If you can speak, you can breath,’ a refrain Chauvin’s defenders have used to suggest police were unaware that Floyd was running out of oxygen. Dr. Tobin dismissed that idea, saying “Certainly, at the moment that you are speaking, you are breathing. But it doesn’t tell you that you’re going to be breathing five seconds later.”