Lung Specialist: Floyd Died on Scene From Lack of Oxygen

Prosecutors in Derek Chauvin’s murder trial called a pulmonologist as an expert witness to discuss the impact of police restraint on George Floyd’s breathing.

Dr. Martin Tobin testifies Thursday, April 8, in the trial of former Minneapolis police officer Derek Chauvin. (Court TV via AP, Pool)

MINNEAPOLIS (CN) — Prosecutors laid into the medical case against Derek Chauvin on Thursday in the former officer’s murder trial for the death of George Floyd, giving jurors a morning of testimony from a prominent Chicago pulmonologist who said Floyd’s death could have happened to anyone. 

That was followed by a toxicologist who assessed the levels of methamphetamine in Floyd’s system as comparable to prescription use and said his fentanyl metabolization wasn’t consistent with an overdose, and a Kentucky police physician who backed up the pulmonologist’s contention that Floyd died of asphyxia while debunking the possibility that he was suffering from “excited delirium,” as one officer suggested on scene. 

“A healthy person, subjected to what Mr. Floyd was subjected to, would have died,” Chicago pulmonologist and critical care physician Martin Tobin said during over four hours of testimony.

Tobin, who hails from Ireland originally and spoke with a slight accent, walked jurors through his evaluation of Floyd’s deadly arrest Thursday morning. He explained the mechanics of breathing in normal conditions, then walked through the various factors preventing Floyd from taking in enough oxygen in the first five and a half minutes that Chauvin knelt on his neck. 

Those factors, he said, included Floyd’s prone position, which allows for less air intake even under normal conditions by reducing the range the lungs have to expand. The pressure on Floyd’s back and position of his handcuffed wrists added to that. “They were forcing his left wrist up into his chest, forcing it in, tight, against his chest, forcing it high up,” Tobin said. “The ability to expand his left side here is enormously impaired.” 

The compression, he said, also tightened a vulnerable spot in the trachea known as the hypopharynx, which Chauvin’s knee served to compress further. 

Asked about the prone position’s usual impacts on breathing, Tobin said that without complicating factors it could impair breathing but not dangerously so.  “The average person, you have so much reserves” of air in the lungs, he said, “but if you have someone with a knee on the neck … then that’s a whole different kettle of fish.”

That became evident, he said, as the 9 minutes and 30 seconds Chauvin spent on Floyd’s neck ticked on. He specifically addressed some of Floyd’s last movements as efforts to improve his air intake. At one point, Floyd moved his head to push his face into the pavement. That position, Tobin said, helped keep his throat and chest open. 

“You can see that Mr. Floyd has his face rammed into the street, because here he’s using his face to try to prop up his chest,” he said. When the side of Floyd’s head hit the street again, Tobin said, his breathing again suffered. “In this position, there’s going to be far greater compression.” 

Tobin pointed to a small kick Floyd made near the end of five and a half minutes and the look on Floyd’s face around the same time as evidence that Floyd was on his way out. “That is something we see as clinicians in patients when they suffer brain injury as a result of a low level of oxygen,” he said of the involuntary leg movement. 

“I work in an ICU, where 40% of our patients die, so I’m extremely familiar with seeing people die, unfortunately,” Tobin said. He said that around 2 minutes and 55 seconds before Chauvin got off of Floyd, jurors could “see the moment when his life leaves his body.” 

That didn’t stop Chauvin, he said. “The knee remained on the neck for another 3 minutes and 2 seconds after we reached the point when there’s not an ounce of oxygen left in [Floyd’s] body.” 

He also had harsh words about something Chauvin said at the scene — that “if you can talk, you can breathe.” 

That’s true, Tobin said, but dangerous. “It’s a true statement, but it gives you an enormous false sense of security. Certainly at the moment you are speaking, you are breathing, but it doesn’t mean that you are going to be breathing five seconds later,” he said.

Judge Peter Cahill called a lunch break before Chauvin’s attorney Eric Nelson could cross-examine Tobin. Nelson and Chauvin quietly took notes for much of the morning, with the occasional objection or request for a sidebar from Nelson.

In one of those sidebars, the attorney apparently objected to Tobin’s habit of speaking directly to jurors and directing them to examine portions of their own necks. Cahill, in response, told Tobin to phrase these directions as requests and informed the jury that while they were welcome to follow along with Tobin, they weren’t obliged to. 

According to a pool reporter in the courtroom, most jurors continued following along with Tobin’s demonstrations anyway. 

Tobin also dismissed the possibility that fentanyl intoxication could have caused Floyd to asphyxiate. “With fentanyl, you expect a 40% reduction of the respiratory rate,” he said. Floyd’s respiratory rate, Tobin explained, was about normal.

He walked the jury through the process of counting Floyd’s breaths as seen on body-camera footage from Chauvin’s colleague J. Alexander Kueng and using that count to calculate respiratory rate. “You can see, when you count it yourself, that the respiratory rate is 22,” he said, concluding that fentanyl was “not having an effect on [Floyd’s] respiratory centers.” 

The problem was not the frequency of Floyd’s breaths but their ability to take in oxygen. Floyd’s oxygen levels, Tobin said, should have been almost three times higher than the level that would render a man of his age and size unconscious. By 8:25 p.m. and 41 seconds, he said, Floyd’s oxygen levels reached zero. 

On cross-examination, Nelson worked to point out that Tobin had a lot more training and time to consider the situation than Chauvin had.

“It’s fair to say that the training of the Minneapolis Police Department in terms of medical care is nowhere close to your level of expertise,” he said. Tobin acknowledged it. 

“You’ve had the luxury of slowing things down, going into slow motion, still-framing various times, yes?” Nelson continued. 

“I don’t know the total amount of time that I’ve spent, but it’s substantial,” Tobin replied. 

Nelson pointed to a paragraph in Tobin’s report in which he said doctors also had trouble diagnosing a different condition, hyperventilation, when patients complained that they couldn’t breathe.

“People, such as yourself, who attended medical school. Talented men and women, who go to college and go on to medical school, they sometimes have problems with this,” he said. “[Patients] are coming in and they’re articulating to their physician ‘I can’t breathe,’ and the physicians confuse this issue. They blame the patient.” 

Tobin quibbled over Nelson’s word choice but agreed that it could be a tricky issue. “I don’t know if they blame the patient, but they miss the diagnosis.” 

Tobin was followed by Daniel Isenschmid, whose lab in Pennsylvania processed Floyd’s blood at the request of the Hennepin County Medical Examiner. He compared Floyd’s blood fentanyl levels — 11 nanograms per milliliter — after death to other cases the lab had studied that year, along with the quantity of norfentanyl. 

Norfentany, Isenschmid explained, is a compound created when the body metabolizes fentanyl. Floyd had a blood norfentanyl concentration of 5.6 nanograms per milliliter, he said.

That level “shows that some of the fentanyl was metabolized to norfentanyl. It also could mean that it was previously existing norfentanyl with additional fentanyl on top of that,” he explained.

Asked how this compared to fentanyl overdoses, he said that norfentanyl didn’t usually appear in fentanyl overdose cases. “After a very acute fentanyl intoxication, the body doesn’t have time to break it down.”  

He compared Floyd’s levels of methamphetamine (19 nanograms per milliliter), fentanyl and norfentanyl to those seen in death investigations and in DUI investigations. The methamphetamine, he said, compared to the bottom 6% of levels seen in DUI cases. The average for those cases was around 378 nanograms per milliliter. 

The amount of amphetamine, meth’s analogue to norfentanyl, was so low in Floyd’s blood as to be negligible, Isenschmid said. 

Nelson, who complained in court of losing his voice, stumbled a handful of times during cross examination, joking with Tobin that he’d been “taken by” the Irishman’s accent. “You’re trying to really confuse me, Mr. Nelson,” Tobin quipped when the attorney mixed up a series of figures in a question. 

“I can honestly say it’s been a long week,” Nelson replied. 

That was underscored later when Nelson stopped the proceedings to announce that he hadn’t received an updated copy of a presentation prosecutors had walked through with Isenschmid. He eventually found the update, saying he’d likely mistaken it for a duplicate. 

Continuing to cross-examine Isenschmid, Nelson worked to cast doubt on the lab’s data. “We can’t differentiate what the actual cause or manner of death was in any one of these cases?” he asked. Isenschmid confirmed that he couldn’t. 

“We have no frame of reference,” Nelson continued. “Did they die from fentanyl overdose, or from something else? We have no context.” 

Prosecutors closed out the day with another expert medical witness, this one with a background of working with law enforcement. Dr. William Smock, who introduced himself as Bill on the stand, is the in-house doctor of the Louisville Metro Police Department in Kentucky. He made similar findings to Tobin’s on Floyd’s cause of death. 

“You will hear his voice get weaker and weaker, and you will see him lose facial expression,” he said, walking jurors through body camera footage. “He then goes unconscious, and you will then see what’s called an anoxic seizure.” 

“You can actually see, and hear, the handcuffs shake, and you see the body camera shake when he has an anoxic seizure, further down the line,” Smock continued. 

Prosecutor Jerry Blackwell, questioning Smock, asked him when CPR should have been started on Floyd. 

“Way before it was,” Smock replied, appearing to struggle slightly to say it. “As soon as Mr. Floyd was unconscious, he should have been rolled over. We have documentation, on the video, where the officer says ‘I can’t find a pulse.’” 

“Why?” he asked. 

On cross examination, Nelson pushed against those theories, working to shore up the overdose theory of Floyd’s death he has advocated throughout trial. Smock, on direct examination, had ruled that out on the basis that fentanyl overdoses slow breathing down, rather than causing people to display “air hunger” as Floyd had. 

“Methamphetamine and fentanyl combined is different than a reaction to fentanyl,” Nelson said, adding that “in emergency rooms of late, the number of deaths from methamphetamine and fentanyl combined have increased.” 

Smock said that the reaction could be different, and that “I can’t speak to ‘of late,’ but that wouldn’t surprise me.” 

Nelson also asked about Floyd’s medical history, noting that he had a partially blocked artery prior to his death, and about Floyd’s drug use. “There is no safe level of methamphetamine, is that right?… In terms of street methamphetamine, there is no valid medical basis to have in your system?”

“That’s correct,” Smock said. 

Blackwell also sought to get out ahead of an issue raised Tuesday by a police department witness: excited delirium. The controversial syndrome, recognized by the American College of Emergency Physicians and the National Association of Medical Examiners but not by the World Health Organization, American Medical Association or the American Psychiatric Association, was first mentioned in this case by former officer Thomas Lane, who can be heard on body camera footage expressing concern that Floyd might be experiencing it. 

Critics have argued that excited delirium is ill-defined, and some have gone as far as to call it “medicalized racism” used to justify force against black men. Smock acknowledged the controversy but said he believed that the diagnosis was legitimate and that it wasn’t applicable to Floyd. 

“Excited delirium is a physical and psychiatric state where, because of an imbalance in the brain, a patient will exhibit multiple symptoms. Basically they’re hot, their body is revved up, their heart is revved up, respiration is revved up, superhuman strength, their speech is garbled, they… can’t answer questions, that’s what’s called delirium,” he said. 

“There are varying opinions as to what causes it, what is it… there isn’t 100% agreement on what excited delirium is, but I can tell you, based on my opinion, that it is real.” 

He proceeded to walk through ten symptoms of the condition, among them excessive heat and a tendency to remove clothing, “superhuman” strength, an apparent insensitivity to pain, rapid breathing, an attraction to and tendency to break glass, heavy exertion without tiring and a lack of situational awareness or comprehensible speech. Six are required for diagnosis, and none, he said, applied to Floyd. “Zip.”

Chauvin is on trial for second- and third-degree murder and manslaughter for Floyd’s death. The three other officers who assisted in Floyd’s deadly arrest are scheduled to go to trial in August on aiding-and-abetting charges.

Court is expected to return to session for cross-examination Thursday afternoon.

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