Chauvin Trial Day 14 Wrap-Up: Mistrial Narrowly Avoided, Closing Arguments Monday

Welcome to our ongoing coverage of the Minnesota murder trial of Derek Chauvin, over the in-custody death of George Floyd.  I am Attorney Andrew Branca for Law of Self Defense.

Today was mercifully brief in duration, but packed full of action—at least, for certain lawyer values of “action,” so let’s dive right in.

Two notable events I’ve already discussed in a breaking news post was the decision of the defense to call no further witnesses—and this included waiving the prospect of having Chauvin appear as a witness to testify on his own behalf.

Chauvin elected to assert his 5A right to not testify, and when offered to have the jury instructed that guilt could not be inferred from his not testifying, he affirmed he wanted that instruction given.  You can see my previous write-up of those events, including court room video of that discussion and exchange, here:

BREAKING: Derek Chauvin Will Not Testify, Asserts 5A Privilege

The big surprise of the day, however, was the state’s sudden claim that they had discovered “new evidence” that justified re-calling state expert witness Dr. Martin Tobin, pulmonologist, to the witness stand to rebut some of yesterday’s testimony by defense expert Dr. David Fowler, a forensic pathologist.

The “new evidence” was purportedly just-discovered data on Floyd’s blood oxygen levels when at the Hennepin County Medical Center.

The state wished to have Dr. Tobin testify about that data to rebut suggestions by Dr. Fowler that given the proximity of Floyd’s face to the exhaust of squad car 320, it was possible that Floyd’s carbon monoxide blood concentration could have been as high as 18%–a level Fowler testified was sufficient to be dangerous to Floyd, and a contributing cause to Floyd’s death, given Floyd’s fragile physiology.

As these things tend to go in court, the argument over whether to allow Tobin to be re-called as a witness for this rebuttal purpose took about twice as long as did his actual testimony—but for good reason.

Obviously, this demand for rebuttal by the state, particular on this blood data “discovered” just after Fowler’s testimony ended yesterday afternoon, and with notice provided to the defense only about 5 o’clock in the evening, was about as late in the course of the trial as could be imagined.

Further, the defense expert witness on this subject matter, Dr. Fowler, was presently on a plane flying home while the state was arguing in court for their own expert, Dr. Tobin, to be recalled.

During the discussion about whether Tobin should be permitted to provide additional testimony, the state set out four areas that they wished Tobin to testify about.

First, the state claimed that the Hennepin County Medical Examiner, Dr. Thomas Baker, after hearing Fowler’s testimony yesterday on the carbon dioxide issue, had somehow dug into the hospital’s records and found that Floyd’s blood concentration of CO had, in fact, been measured at the time—but had never been previously produced when the parties had subpoenaed Floyd’s medical records.

The state now wanted these data to be shared with the jury and explained by Dr. Tobin, to rebut Fowler’s claim that Floyd’s CO concentration could have been as high as 18%.

Normally, of course, the state would have been expected to make such arguments in Dr. Tobin’s original testimony, and their failure to do so would not be a good reason to suddenly allow Tobin to re-testify now.

An exception to that normal prohibition on re-testimony, however, can be made if the defense itself had “ambushed” the prosecution with scientific arguments for which they had not provided the state with notice.

Prosecutor Blackwell argued that Fowler’s reference to CO concentrations as high as 18% had never previously been disclosed to the state, and so qualified as just such an “ambush” that justified Tobin’s re-call to the witness stand.

The defense countered that Fowler had explicitly referenced CO as a possible contributor to Floyd’s death in his expert report shared with the state weeks before trial began and had even recommend that the state test the blood for CO concentration.

It was only the state, not the defense, that had possession of the blood.  As a result, the state was on notice with respect to the CO issue, and if they failed to address that issue in a timely manner, that was on them.

Judge Cahill agreed with the defense with respect to this “newly discovered” blood gas level data, and informed the state that if Tobin so much as hinted at this new data, the Judge would order a mistrial had occurred.

That said, Cahill said he would allow Tobin to speak to the CO concentration issue if he only referenced data that had long been available to both parties.  That opened the door to the prosecution having Tobin reference Floyd’s oxygen (rather than carbon monoxide) levels, and use the O level to infer possible CO level.

This is possible because O and CO both compete for the same binding location on hemoglobin, and only one of them can bind any particular hemoglobin protein.  So, a protein bound by O cannot also be available to be bound by CO, and the reverse.

Because the parties were aware that blood gas measurements had indicated that Floyd’s blood had O levels of 98%, it could be inferred that his CO levels could be no greater than the remaining 2%, which was well within normal.

There was also another entirely separate issue that the state also wanted Tobin to provide rebuttal testimony on, and this involved Fowler’s claim yesterday that he had been unable to find any scientific studies supporting Tobin’s earlier claim that the hypopharynx could be narrowed by pressure placed on a person’s back.  Fowler said he had searched the major scientific publication database, known as PubMed, and come up with no results.

The state claimed that Fowler’s reference to this PubMed search was “new evidence” not previously shared with them, again qualifying as “ambush” testimony, and again providing the exception necessary for them to have Dr. Tobin testify on this issue on rebuttal.  The state indicated that Tobin would testify that there were, in fact, a number of scientific papers and studies that supported his claim.

Naturally the defense objected, saying that they would not have any opportunity to research Tobin’s claim of such papers and studies existing, much less of actually reading these materials in order to understand if they supported Tobin’s claim or were subject to effective impeachment.  Further, again, the defense expert witness Fowler was on a plane and not available to the court.

Judge Cahill ruled that Tobin would be permitted to testify as to the existence of such papers on rebuttal, in a summary fashion.

The state also wanted to be permitted to have Dr. Tobin testify again on his earlier claim that the cause of Floyd’s death was hypoxia, or low oxygen, claiming that Dr. Fowler had contested that claim in yesterday’s testimony.

Fowler had claimed that it wasn’t low oxygen induced by positional asphyxia that caused Floyd’s heart to fail, as Tobin had argued, but rather that it was Floyd’s heart failing that had resulted in a low oxygen state.

This was the weakest argument for rebuttal testimony offered by the state.  Really, both Tobin and Fowler agreed that Floyd had evidenced a low oxygen state by various symptoms, such as a particular convulsive leg kick.

Their only disagreement was the precise mechanism that had led to that low oxygen state—Tobin claimed positional asphyxia as the cause, and Fowler claimed cardiac arrest as the cause.

Cahill ruled that Tobin would not be permitted to testify as to this issue on rebuttal.

So, in the end, Tobin was permitted to speak to the issue of inferring a maximum CO concentration in Floyd’s blood of no more than 2% based on the measured O level of 98%, and to inform the jury that he was aware of some 12 to 20 scientific papers that supported the notion that smaller lung volume resulted in a narrowing of the hypopharynx.

Here is that discussion among the parties and Judge Cahill:

State Direct Questioning of Tobin Rebuttal

That direct questioning on rebuttal was conducted by Prosecutor Blackwell and took only about 8 minutes.  Excitement, of the legal type, occurred about four minutes into direct when Tobin appeared to reference the blood gas data that Cahill had cautioned would result in a mistrial.

Nelson immediately objected, and the court went into a couple of minutes of sidebar, during which I’m sure the defense was asking for a mistrial.

Frankly, in my professional opinion, a mistrial in this case would be entirely warranted, if not from this particular incident in isolation, then from the accumulated harms done to the defense by the state’s untimely dropping of thousands of exhibits on the defense even as the trial proper was taking place, averaging nearly 500 new exhibits each day of the trial.

At the end of that sidebar, however, Blackwell returned to continue his direct of Tobin, so no mistrial, and presumably he was cautioned to avoid mention of the prohibited blood gas data.

Defense Cross-Examination of Tobin Rebuttal

After Tobin’s rebuttal testimony on direct, there was another lengthy pause in the proceedings, conducted off microphone (and perhaps even in the judge’s chambers rather than in the court room), during which I’m confident that Nelson was once again arguing for a mistrial.

Apparently that argument was to no avail, however, because Nelson did return and conduct cross-examination of Tobin.

Without any real way to prepare for this unexpected testimony, there really wasn’t much he could accomplish.  As a natural consequence of this constraint, his cross took only about two minutes, and you can view that here:

That ended Tobin’s rebuttal testimony.

Judge Advises Jury to Expect Closing & Deliberations Monday

At this point the state and defense both made the final announcement that they were resting their case in chief, and Judge Cahill turned his attention to the jury.

They would be dismissed for the day, and until Monday at 9:00am CT, at which time they would return to court to hear the closing arguments of the state and the defense, receive their jury instructions, and begin their deliberations.  They were reminded that they were to be sequestered during deliberations, and so were cautioned to “pack a bag.”

On the topic of how much to pack, Cahill suggested that they plan for a long sequestration, and hope it turns out to be a short one, but that ultimately only the jury could decide how long deliberations would take.

The jury was then dismissed.

Discussion re: Charging Conference (Jury Instructions)

After the jury had left, there was a brief discussion about the charge conference for this trial.  The charge conference is where the parties meet with the judge to iron out the precise jury instructions to be given to the jury to guide them in their deliberations.

Obviously, because those instructions guide the jury to either a guilty or not guilty verdict, each party has an interest in trying to bias those instructions in their own favor, both by ensuring that particular desirable instructions are included among those given to the jury, as well as that any customization of the instructions be favorable to their own interests.

Minnesota, like most states, has standardized jury instructions for criminal trials, but standardized instructions are always subject to some customization by a trial judge to best fit the particular facts and legal arguments in a given trial.

I’ve covered the relevant standardized jury instructions likely in this case in a blog post early this week, here:

LIVE: Chauvin Trial Day 12 – Meet the Jury Instructions, Bring On The Defense Case

The selection of the specific instructions to be given to the jury, and discussion of any possible customization of those instructions, are what is hashed out during the charge conference.

Unfortunately for us, Cahill announced that the charge conference in this case will take place in chambers, so will not be subject to observation.  I do expect we will be able to observe the actual reading of the instructions to the jury in court on Monday, however, and if I obtain physical copies of those final jury instructions, I’ll share them, as well.

UPDATE: State & Defense Discussion of Jury Instructions with Judge Cahill [AFB]

Hey, folks.  Apparently the parties spent a couple of hours with Judge Cahill in chambers discussing the jury instructions, outside of the view of cameras, and then came back into the courtroom to establish a 30-minute summary of key points for the court record.–and that 30-minute in-court discussion was made publicly available.

Accordingly, here’s the video of that in-court discussion:

And that wraps up our coverage of the Chauvin trial for today, folks. Expect to see us back with live coverage of the court’s proceedings on Monday morning, and perhaps a post to carry us over the weekend if some interesting topic strikes my fancy in the interim.

Course Special: Lawful Defense Against Rioters, Looters, and Arsonists

Before I go, in view of the ongoing riots raging presently in Minneapolis, and likely to explode across the nation when this case arrives at a verdict (or mistrial), I’ve also taken the liberty of putting together a special opportunity to access our best-selling course, “Lawful Defense Against Rioters, Looters, and Arsonists,” available in both online streamed and DVD formats.  You can learn more about that course, by clicking here.

And thanks, as always, to both Legal Insurrection and CCW Safe for the support that makes my coverage of this case possible.


Attorney Andrew F. Branca
Law of Self Defense LLC

Attorney Andrew F. Branca’s legal practice has specialized exclusively in use-of-force law for thirty years.  Andrew provides use-of-force legal consultancy services to attorneys across the country, as well as near-daily use-of-force law insight, expertise, and education to lawyers and non-lawyers alike. He wrote the first edition of the “Law of Self Defense” in 1997, which you can now order in its current edition for just the price of shipping and handling by clicking here.  To know YOUR state’s use-of-force laws in an actionable way that will keep you safer physically and legally, take our state-specific advanced use of force class either streamed online or via a shipped DVD with a 100% no-question- asked money-back guarantee, here:  Law of Self Defense State Specific Use-Of-Force Class.

[Featured image is a screen capture from video of today’s court proceedings in MN v. Chauvin.]


31 thoughts on “Chauvin Trial Day 14 Wrap-Up: Mistrial Narrowly Avoided, Closing Arguments Monday”

  1. Something is a bit wrong. If the oxygen saturation was 98%, then there was not low oxygen. 98% is most reasonable. They let you out of the hospital if you can do 91% walking up and down the hall. Under 80% is the danger zone.

    1. I found it confusing too. Is it CPR that refilled oxygen supplies? If yes, how can any blood tests be used to determine the cause of death with certainty.

      Frankly, CO is not something that should have been a big issue. The Jury could claim it is officers fault to place a suspect near the car exhaust and attribute even more guilt. On the other hand, almost a mistrial. That’s an unexpected turn.

      1. CPR and the supply of 100% oxygen that would of reduced any CO. The defense witness should of stated there was no accurate way to measure if CO actually effected Floyd due to the medical treated he received prior to the blood tests being done. Probably should of just not brought up the issue.

        1. I agree. In fact, the treatment for CO poisoning is hyperbaric (greater than atmospheric pressure) oxygen, just as divers with the bends are treated. In fact, HCMC has a hyperbaric chamber they use, although not in Floyd’s case. In the absence of a hyperbaric chamber, giving 100% oxygen is an alternative, trying to compete for the binding sites of hemoglobin so that carboxyhemoglobin gets converted to oxyhemoglobin. I assume Floyd was intubated as a last resort and given 100% oxygen, but obviously too late to bring him back.

    2. Yes, this is confusing to me.

      There are two possibilities in depriving the brain of oxygen. One is you prevent blood going to the brain. A “blood choke.” You constrict the blood vessels in the neck sending blood to the brain. This would be VERY difficult to do with a knee to the back and shoulder and difficult with a knee on the neck as only one side would be effectively constricted. But presumably the blood O2 levels would remain high or at “normal levels.” Earlier testimony makes me very uncertain that this happened to George Floyd.
      The second is you deprive the lungs of the ability to respirate and exchange oxygen and CO2. That seems plausible with a knee to the back and shoulder though I’d expect some bruising etc to show in autopsy but maybe not?? If this is the case though wouldn’t the blood O2 level be much lower than 98%?? Would the EMS team and or the hospital be able to infuse the blood with that Oxygen level during CPR etc and still lose him? If so then wouldn’t that process rid the CO2 levels as well?
      Just this discussion seems to create a level or doubt that would make it difficult for me to say that it was Officer Chauvins knee on George Floyd’s back and shoulder or neck that beyond a reasonable doubt killed him.

    3. My thoughts exactly. How would someone die from low blood oxygen level (asphyxiation) and then have high blood oxygen in the hospital later. Could Floyd’s heart have stopped for a time, ceasing to circulate that well oxygenated blood? The belated CPR might then have gotten some circulation going and even perhaps restarted the heart, but could have been too late to do any good.

  2. Nelson did a terrible recross of states rebuttal witness. If he had remembered his owns witness testimony, is stated CO poisoning is reversible by providing 100% oxygen and CO would dissipate after an hour to an hour and a half. Wow, look at that time, 8pm to 9:30pm when the panels were taken. Clearly the 100% Floyd was getting and the blood being circulated cleared out and wouldn’t be found on the panel. The defense witness messed up this point yesterday, he should have been clear the panel would have only showed this if Floyd wasn’t given CPR and oxygen. He jumped too fast to the conclusion and how to show the conclusion without considering all the factors in the case.

    1. Nelson probably wanted to limit the time Tobin is in front of the Jury and spend all the efforts of the day on the Jury instructions and then move to prepare the closing. Long weekend will diminish anything happening on Thu and if they can bring sufficiently plausible explanations to all the rebuttals, as well as raise up the 98% O2 doubts during closing, that might win some ground. If that’s not the case and closing is not offering any new angle (using only existing evidences, of course) and, on top of that, Chauvin pleading 5th (no matter Jury instructions), it will be hard to acquit of all charges.

  3. I’ll just repeat here what I commented above, namely that the 98% oxygen saturation was an artefact of Floyd being intubated and mechanically ventilated with 100% oxygen, standard treatment for cardiac arrest in any ER. What really matters is the cellular level of oxygen and the changes in acid/base chemistry attendant to that, which then go on to throw out the balance of electrolytes like potassium. At a certain point, one can be ventilating a corpse and not be able to revive him.

  4. I could be wrong, but I believe all the expert witnesses who were supposed to be “medical experts” testified that an examination of the body of George Floyd revealed that there was no physical evidence of a blood choke or an air choke, period. For some reason unknown to me, all the medical experts for the prosecution were allowed to speculate without any physical evidence to support the conclusion, or any expertise in the field of judicious use of physical force, that the physical force used by Chauvin and others was sufficiently forceful to be deadly physical force and that the deadly physical force must have caused the death of George Floyd. You know how the left is, never let the facts get in the way of an opinion that fits your agenda.

    1. Attorney Andrew Branca

      I wanted to take a moment to respond to you generally, not so much this particular comment, but there have been several of your comments recently that made excellent legal points, worthy of response, but I’ve just been swamped doing the live coverage of this trial. Your comments have deserved better than a non-response, and I apologize for that, but there are only so many hours in a day.
      On the issue of the state experts being permitted to speculate to their heart’s content, while defense witness Fowler was treated with contempt for merely making reasonable inferences from the available evidence, 100% correct.
      One area I would caution on is that this is not a traditional justified use of force case, so the standards that would apply there don’t necessarily apply here. This will be easier to discuss once the jury instructions are finalized, hopefully tonight or this weekend, and whenever I can get them in hand, but this case is not really amenable to my usual 5 elements analysis because it’s not a traditional self-defense scenario.
      As one example of how this case differs from a more traditional self-defense case, a typical self-defense case requires the defendant to not have been the initial physical aggressor. This case, however, involves police, and police are legally privileged to be the initial physical aggressor, if necessary to compel compliance with the law.
      Again, however, a more structured discussion of these issues will be much easier once we have a set of final jury instructions to use as a legal framework for that discussion.
      Thanks a ton, to you, and everyone else commenting here, for your attention to this case, and to my own modest commentary, as well as your own insight into the legal dynamics of this case. It’s all of you who really make it possible for me to do this work at this level of intensity and focus.


  5. It seems to me that it was impossible for Chauvin to be properly represented given the overwhelming resources and tactics of the State and D.A., and the limits of what one attorney can absorb and convey. The high handed tactics to exhaust Nelson and not allow him proper time to prepare is unconscionable. Chauvin’s apparently limited budget (given the quality and sparseness of their “expert” witnesses) it wasn’t close to being just.

    My hope is that there will be a hung jury on all counts because it is impossible for a finding of not-guilty. Just the overwhelming emotional subtext and repeated unsupported declarations by “experts” is gong to sway the laypersons jury.

    Should, by some miracle, there be a hung jury hopefully a new trial will be properly administered and the defense come up with at LEAST two qualified use of force experts and two fentanyl experienced pathologists.

    The mob is going to win this one.

    1. Attorney Andrew Branca

      I concur. If Cauvin is convicted I can easily imagine him bringing an appeal based on ineffective assistance of counsel, and Nelson testifying on his behalf. “Yes, I was ineffective. The state made it IMPOSSIBLE for me to be EFFECTIVE.”

    2. I disagree that it is impossible for a finding of not-guilty. On the basis of the evidence presented, I don’t think there is sufficient evidence for probable cause to believe Chauvin is guilty of any of the crimes charged, much less guilty beyond a reasonable doubt. I don’t even think there is sufficient evidence to find him guilty of any of the lesser included offenses of second degree murder, which appear to be third degree and/or fifth degree assault. I do agree that it is unreasonable to think that this jury in these circumstances would actually find Chauvin not guilty of any of the charges or lesser included offenses.

      1. To clarify, it is not impossible given the evidence BUT it is impossible given the jury’s knowledge that a not guilty verdict on all counts would spawn more riots. No matter what their doubts I believe that a 3rd degree murder conviction could happen.

        As I said, a hung jury would give Chauvin a second chance. Now we will see if the others do better now that they have seen the cards played against Chauvin.

  6. Charles McCarthy

    If this case was in a vacuum and based on the evidence Chauvin probably would be acquitted. In today’s world he will be found guilty, probably of the most serious charges. I agree with everyones legal reasoning but predicting the outcome is easy. Chauvin is screwed. Another prediction: Appeals will fail for fear of reprisals. Even appellate courts in this case will bow to the mob. I hope I am wrong but I am a good predicter.

  7. After re-reading the autopsy report, I’m surprised that the defense went into the weeds with Carbon monoxide but never mentioned that Floyd had Sickle Cell trait and 38% of his hemoglobin was Hemoglobin S. They could have mentioned blood flow changes due to hypoxia and Hemoglobin S, reports of sudden death with severe exercise and Sickle trait, etc.

    I still think that cause of death is undetermined but most likely due to cardiac demand ischemia>ventricular arrhythmia>death.

    1. Attorney Andrew Branca

      Sickle-cell “trait” is largely innocuous. It’s the one-gene defect version of the genetic disorder–the good gene takes up the slack, and limits physiological consequences.
      Sickle-cell “anemia” is what is generally recognized as a serious disorder. Both genes are bad, and hemoglobin is badly disfigured.
      Floyd had “trait,” not “anemia.”

  8. thomas deconcini

    I just bought the DVD on RIOTS !! I cant afford it , but I cant afford to not know what it says ! thanks for making it , !! I hope you will cover Kyle Rittenhouse trial !

  9. This case is more confusing than it need be because Minnesota’s attempts to codify the common law of homicide are pretty poor and because the charges brought against Chauvin under Minnesota law are improper under Minnesota law.

    By charging Chauvin with unintentionally (accidentally) killing George Floyd with a use of physical force the state conceded that Chauvin’s use of physical force was nondeadly. Police officers have permission of the law to make an arrest for a felony offense on probable cause and to use nondeadly force to make such arrest or to prevent an escape from custody after the arrest has been made, and for other purposes.

    Blackstone said that when a man doing a lawful act by lawful means undesignedly kills another, the homicide falls into the category of excusable homicide and it is excused on the grounds of misfortune.

    Since the state hasn’t met its burden of going forward with the evidence that the arrest was unlawful, or in the alternative met its burden of going forward with the evidence that the nondeadly force used to make the arrest was unlawful, Chauvin is entitled to a directed verdict of not guilty.

    The state cannot meet its burden of producing evidence the nondeadly force was unlawful by simply claiming the force it has conceded was nondeadly was actually deadly force. People are undesignedly killed with a use of lawful nondeadly force quite often, the fact that they are killed doesn’t make the lawful use of nondeadly force a use of unlawful deadly force.

  10. Andrew, why are people saying Dick Chauvin “took the fifth?” Did the prosecution call him as a witness? Did the defense call him as a witness? Did the judge call him as a witness? I never heard it called “taking the fifth” simply because you chose not to call yourself as a defense witness. Why would you need to “take the fifth” if you hadn’t been called as a witness?

    I personally think he should have took the stand and explained what he saw, and what he inferred or perceived from what he saw, what was his reasons for believing his use of nondeadly force was necessary in the circumstances that were forced upon him, and what his intent in using such force actually was. He could have also testified as to the amount of force he was applying to restrain Floyd, and as to the amount of force Floyd was using to resist restraint, as these are things that nobody knows except Chauvin. Of course I guess he may have though his image was just to bad and that his testimony would inflame the jury.

    1. Attorney Andrew Branca

      It’s just the way the courts handle the issue procedurally, and to ensure that a defendant can’t later claim that he was denied the opportunity to testify on his own behalf.

      You know you can testify? Yes.
      Discussed it with your lawyer? Yes.
      More than once? Yes.
      And now sitting here, you’re telling the court you don’t want to testify? Yes.
      You also know you have a 5A right to not be compelled to testify? Yes.
      You are asserting that right to not be compelled to testify? Yes.
      You’re ABSOLUTELY SURE don’t want to testify? Yes.

      It’s just so there’s no remaining possible doubt about the issue.

  11. Sorry, I’m late to the discussion. I’ve been out of town for a few days, so here’s my 2 cents. There seems to be some “misunderstanding” about the relationship of arterial oxygen saturation measurement and the effect of levels of carboxyhemoglobin in blood. Firstly, oxygen saturation in a blood gas sample is not commonly directly measured. It is calculated from the Pa02 (partial pressure of oxygen) using the Severinghaus equation (See: ) as its basis and for many years has been calculated using a form of the Siggaard-Andersen nomogram that takes into account such things as the effects of pH and PaC02 on the oxygen saturation/disassociation curve. The important point here is that the Sa02 (saturation of 02 ) as calculated does not necessarily indicate the content of oxygen in the blood as that is also a product of the hemoglobin available for transport ((usually referenced by the hematocrit (percentage if red blood cells in whole blood) in clinical settings)). Elevated carboxyhemoglobin levels effectively reduce the number of hemoglobin molecules from exchanging oxygen. It’s similar to a state of anemia where the total number of red cells is reduced. That in and of itself doesn’t lower the Pa02 from which the saturation is calculated. So, saying that, if the saturation is 98% leaves only 2% for other gases is a fallacy as that number is calculated from the partial pressure of the gas that isn’t dependent on the actual oxygen carrying capacity of the blood. When I worked in Denver, I routinely saw carboxyhemoglobin levels in excess of 10% in smoking truck drivers who frequently traversed the Eisenhower tunnel. Their O2 saturations were usually normal for the altitude (not including other complicating clinical factors). It is not uncommon to see normal or even elevated saturations (those receiving supplemental oxygen) in anemic patients. “Dr.” Tobin, is either poorly informed or willfully ignorant of these facts. Also, the testimony that Floyd’s oxygen levels were categorically “0” is ridiculous as he had no way of knowing that value simply from watching a video and seeing the subject become unconscious. He could have said that they were below life sustaining levels and been more correct. However, I seem to remember someone saying that Floyd’s saturation was 98%. That neither jives with the “0” level or the comment that he died of asphyxia unless that measurement was the result of some rather efficient resuscitation effort.
    As another aside, I noticed that they seem to be focused on myocardial ischemia or infarction as the etiology of a possible cardiac arrest. That isn’t the only cause of cardiac arrest. There is also the possibility of a fatal arrhythmia (or dysrhythmia) brought on by cardiac sensitivity to exogenous drugs and release of epinephrine. I don’t see why a transient ischemic episode contributing to this factor can be ruled out as there is ample evidence of this possibility and wouldn’t leave any residual physical finding on autopsy.

  12. The whole issue of the late presentation of the arterial blood gas (ABG) seems odd.

    I never worked in a coroner or ME’s office, but I did work in a pulmonary physician’s office. Usual blood panels (usually consisting of 12 or more test values) were drawn from venous blood (blood returning to the heart from the tissues), while blood gas (for PaCO(2) and PaO(2) ) were drawn from arterial blood (blood coming from the heart going to the tissues). For the purposes of testing for critical BG’s (CO(2) and O(2)) venous and arterial blood are not interchangeable.

    The lawyer for the prosecution stated that the blood gases were drawn as part of a routine panel. If it is common for ABGs to drawn at autopsy, then the ME (Baker) should have known that and supplied the information when originally requested by the defense. If it were not usual, and ordered specially by Baker, he should have known that as well.

    Since the prosecution could not refer to the “newly discovered” (arterial ?) blood gasses, I wonder if they were using the O(2) saturation (98%) from the IR pulse/oximeter as the basis for claiming that only 0%-2% was “leftover” for CO. Of course, the pulse/oximiter cannot determine the difference in Hb bound by CO or O(2), and CO bound by Hb gives a false (higher) reading for O(2) saturation.

    1. Yes, this report doesn’t make since on a number of levels. My concern was that I this “expert”, one who self acclaims almost clairvoyant medical skill in “precisely” calculating physiological parameters from a video, could make such a glaringly erroneous statement. It raised doubt about other statements he has made. You are correct in that the pathologist would have drawn venous samples, which would have been useful in estimating acid/base status, electrolytes, and toxicology, which may have given clues about the state of the patient at and just prior to the time of death. It is difficult to obtain arterial samples from pulse-less patients, I know this from personal experience. You are correct about pulse oximetry, it would have read higher than actual saturation as the absorption curves for oxy- and carboxyhemoglobin overlap given a falsely high result. Again I don’t know how you would get a pulse oxymeter to work on a pulse-less patient. While is is possible to assess the metabolic state of a patient form the acid/base status in a mixed venous sample and thusly estimate the extent of perfusion and oxygenation in the peripheral circulation, you cannot “measure” or even estimate the level of carboxyhemoglobin from a saturation, venous or otherwise. It is really too bad that the defense didn’t have an expert to counter these claims based on the specifics that he categorically stated using his claims of precision and certainty.

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