This is a writeup of the case for the innocence of Derek Chauvin considering the revelations of the trial up to the point at which the prosecution rested its case. I’m going to cover this from the side of the defense because it has been criminally underreported in the media, as well as because I am sympathetic to it—I have written a case for Chauvin’s innocence before, and much of what I wrote has already been vindicated in the trial. But remember that all of this refers to testimony before the defense has called a single witness.
Caveat: I did not watch all of the proceedings. I skipped all the sentimental witnesses, as well as the eyewitnesses, whose testimony is obviated by the ample video documentation. I watched most of the technical testimony—not all, but enough to understand the case in about as much detail as an interested layman can.
I’m going to divide the body of this writeup into two sections: the police witnesses and the medical witnesses.
The police witnesses
The police witnesses testified regarding whether Chauvin acted appropriately and reasonably, in the context of police procedures and justifiable decisions in the field. Though, as witnesses for the prosecution, the general opinions of these witnesses were unfavorable of Chauvin’s conduct, they helped to establish various points favorable to the defense. They agreed beyond the point of reasonable questioning on the following:
The restraint applied to George Floyd, known as the maximal restraint technique, is not only explicitly permitted by the MPD but officers have received training in it
The restraint is not a chokehold and does not constitute lethal force
The restraint was correctly applied with respect to force and position (what is questioned is how long it was applied for)
George Floyd was at one point actively resisting arrest
The restraint was initially a reasonable use of force
These points being established make the prosecution’s case a lot more limited than the general public seems to think it is. It must establish that, at some point in the period for which George Floyd was restrained, it became unreasonable to maintain the restraint (which I referred to, in my original post, as a judgment call).
The defense was particularly effective in establishing reasonable doubt here. Chauvin’s attorney, Eric Nelson, got various admissions from the expert witnesses regarding how there are no objectively established criteria to determine when it’s safe to release a suspect from a restraint; that a handcuffed suspect still poses a potential threat; that suspects often feign illness or emergencies to avoid arrest (which is a form of passive resistance); and that various factors may reasonably bear on an officer’s decision in this respect, such as the size of the suspect, his mental state including intoxication, his resistance before restraint, the presence of a hostile crowd and so on.
The cross-examination of the police experts was not a definitive win for the defense, but it established plenty of grounds for reasonable doubt. Surely Nelson will call expert witnesses willing to defend that maintaining the restraint was reasonable, and disagreement among experts should, in general, go to the defense.
The medical witnesses
While the hurdle with the police experts was to establish Chauvin acted unreasonably, the medical experts needed to establish that Chauvin effectively caused the death of George Floyd. This is a much more complicated question.
First, it bears mentioning that death by constriction of the carotids is ruled out—it doesn’t fit the timing, and it is clear from the video that Chauvin did not constrict both of the carotids, which would have been necessary for death. The prosecution’s case was built around the hypothesis of asphyxia.
The prosecution did not explicitly or entirely abandon the hypothesis that the knee to the neck caused Floyd’s death. Dr. Tobin explained how position can constrict the hypopharynx, a small tube of soft tissue above the larynx, in a way that would not show up in the autopsy. However, Tobin’s own testimony rendered this point moot; he agreed that “if you can speak, you can breathe” is true insofar as the upper airways are concerned—Floyd’s continuous protestations that he couldn’t breathe did mean his airways were clear, if not entirely, then enough.
The meat of Tobin’s testimony was about lung capacity—that the combination of position and pressure to Floyd’s back reduced his lung capacity until his air reserves (and then blood oxygenation) became critically low. Though he and other medical witnesses insinuated the neck compression may have played a role, these are not additive conditions; either airway restriction or lung capacity must be the limiting factor.
Dr. Tobin struck me, frankly, as a hack. He based his conclusions on a theoretical model claiming far too much precision and denied that individual factors could significantly alter the results, making his point with rather too many graphics and animations.
I got the same feeling when he was discussing studies like this one, which placed participants in prone restraint with weights of up to 100 lbs on their back and show no significant changes in blood oxygenation after 3 minutes; Tobin claimed the study was not representative in part because it used plates for the weight, and the knee, having a much smaller area of contact, exerts pressure on a different “order of magnitude”. Hopefully it’s obvious that, though this is technically true, the pressure to the lungs will be mediated by redistribution of the force by the ribcage and other rigid structures; if it makes any difference at all, it is certainly not of an order of magnitude.
Dr. Lindsey Thomas, the former Hennepin County medical examiner whom I generally found more credible than Tobin, also commented on these studies, claiming they “bear no resemblance to real-world situations”, which is absurd on its face. Neither she nor Tobin pointed to a clear mechanism by which Floyd’s situation would have caused positional asphyxia and these studies would not except time. Note that Floyd lost consciousness in about 5 minutes, compared to the study’s three. A different study did go all the way to 5, though, still finding no significant compromise of blood oxygenation. (The prosecution tried to fudge on this point by claiming the whole period of restraint as relevant, even though Floyd was already unconscious (or dead) for about half of it.) Nelson also brought up a study from Canada that looked at thousands of instances of use of the prone restraint with zero deaths; Dr. Thomas said that it was not consistent with what is routinely observed by medical examiners. However, similar studies with similar results have been done in the US as well (for instance) and, as Nelson tried but failed to elicit from her, positional asphyxia is a diagnosis of exclusion, which itself should be a red flag that it is inherently indeterminate. It literally needs to be presumed in the absence of other observable causes.
Another medical witness, Dr. Bill Smock, made a very credible case that Floyd was not suffering from excited delirium, assessing the criteria one by one. (I said in my own earlier writeup that excited delirium was a bad hypothesis.) Smock also argued from observation that Floyd died of asphyxia.
The weaknesses I pointed out notwithstanding, in my layman’s estimation the prosecution made a strong case that Floyd died of asphyxia. They also made a strong case that this asphyxia did not result from the common mechanism of opioid respiratory depression, in which death is preceded by coma and, in the words of Dr. Smock, does not cause “air hunger”. I will note that this does not apply to my own pet theory that Floyd died of a distinct mechanism of fentanyl overdose known as wooden chest syndrome, which is not necessarily associated with unconsciousness and absolutely does cause air hunger.
Chauvin’s lawyer, Nelson, barely touched on wooden chest with Tobin, and in general referred to the mechanism of respiratory depression instead, I’m not sure why. His main thesis, though, is that Floyd died of a heart episode. This also led him to put more weight on the meth in Floyd’s blood; though he got rote admissions that “there is no known safe dosage of meth” from the doctors, they broadly agreed that it was a very small dose, unlikely to be significant. One of the main witnesses to this effect was forensic toxicologist Daniel Isenschmid, who compared Floyd’s meth blood concentration to those of DUI arrestees, showing it to be in the very low end.
Isenschmid also made an argument based on the concentration of norfentanyl in Floyd’s blood. Norfentanyl is a metabolite of fentanyl, and the concentration would indicate Floyd had taken fentanyl some time prior to his death; overdoses are highly acute, and norfentanyl concentration in OD cases tends to be very low. However, given videos from inside cup foods and various testimonies, Floyd had been high before police arrived; the defense’s thesis is that Floyd took another dose during the interaction.
My own hypothesis (and not just mine) was that Floyd had swallowed his stash as police approached, but a newly released fact caused me to revise this conclusion: two partly chewed speedball pills (containing fentanyl and meth) were found in the back of the squad car with Floyd’s saliva, presumably dropped or spit out in the brief moments during which Floyd was in the vehicle. So Floyd likely put the pills in his mouth as the police arrived without swallowing, and the dissolving pills dosed him during the interaction with the police, until he was put in the police car. In addition to providing physical evidence for a thesis that was previously only circumstantial, it also makes more sense of the timeline of his death as overdose, which even in the case of wooden chest is typically highly acute (ie within a few minutes).
Dr. Andrew Baker, the medical examiner who performed Floyd’s autopsy, was, surprisingly, excellent for the defense. Much was made in the media about how he ruled the death a “homicide”, but he clarified that this has a particular technical sense in a death certificate that is distinct from the legal; he believes the restraint played a role in Floyd’s death, but not necessarily a culpable one. Specifically, he said that in his opinion Floyd died of a cardiac event resulting from a combination of factors, but it was the stress of the restraint, rather than asphyxia, that caused it.
It’s possible that Nelson was banking on this being the bombshell that would make his case. I’m less certain it will, given the strong argument the prosecution made for asphyxia (and Nelson seemed most rattled on the first day of medical testimony, after riding high with the police experts). It certainly does somewhat undermine the case for the prosecution, but a lot will ride on how convincing his own expert witnesses will be in arguing, presumably, for the hypothesis of a cardiac event.
As I’ve intimated, I’m still convinced fentanyl overdose via wooden chest syndrome is the most likely cause of death, and it was a misstep on the part of the defense to insist on fent overdose simpliciter as often as it did. Still, the defense has presented a solid case so far, especially given that it was built exclusively on the witnesses for the prosecution. Obviously this is a case with many factors beyond the court proceedings bearing on it, but on the merits, there’s a fair chance for an acquittal.