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Defense Questions Pathology Expert in Chauvin Trial. Aired 1- 1:30p ET

Aired April 14, 2021 - 13:00   ET



DR. DAVID FOWLER, FORMER CHIEF MEDICAL EXAMINER, MARYLAND DEPARTMENT OF HEALTH: So, people typically start to get a little confused, disoriented, they may have visual changes. People describe it as spots of light, a gray curtain coming down. So there are visual abnormalities that people describe and complain of. They have become incoherent. They have difficulty speaking.

What is happening with hypoxia is your brain is getting progressively short of oxygen. And so you are getting decreased function of your brain. And some of those are going to mimic intoxication by other sources.

ERIC NELSON, DEFENSE ATTORNEY: Did Mr. Floyd, based in your review, complained such visual changes?

FOWLER: No, he complained of shortness of breath but there was no indication that he made any statements that he was having difficulty seeing things?

NELSON: Is shortness of breath one of those things you would expect to see in hypoxia?


NELSON: What causes that feeling of shortness of breath in a hypoxia situation?

FOWLER: Again, if we are looking at hypoxia of the brain, which gives the person the sense that they need to breathe faster, breathe harder, and they are short of breath, and that can be caused by the inability to get oxygen or air into the lungs, so an obstruction, and/or something that interferes with the airway or affects the ability to move the lungs. So it can be respiratory or it can be cardiovascular.

And you can get shortness of breath with a heart attack. You can get shortness of breath with other vascular abnormalities. So, therefore, it's not a good discriminator, it doesn't help you separate out whether or not there was a respiratory problem, this is a distribution problem of the oxygen. Because what you're looking at is air coming into the lungs and then the heart distribute it.

And if you have anything which interferes with the distribution of air from outside your body to the absorption through the heart and getting to the brain, all the brain sees is, I have not got enough oxygen, and you get the sense of I am short of breath.

NELSON: And do you get that same sensation from cardiac functions?

FOWLER: Yes, I just mentioned that, yes.

NELSON: I'm sorry. In your review of the videos, did Mr. Floyd appear confused?

FOWLER: He -- not confused to the time and place and disoriented, no.

NELSON: Did you observe breathing patterns?


NELSON: How would you estimate his breathing to -- what was the rate of his breathing?

FOWLER: I think my estimation was very similar to previous experts, about 20 to 25 breaths a minute.

NELSON: And if somebody is experiencing hypoxia, how would that affect the rate of breathing?

FOWLER: Typically, when you are short of breath, you breathe faster, faster and faster.

NELSON: Is 22 to 25 breaths per minute considered rapid breathing?

FOWLER: It is faster than being at rest. And, typically, at rest, we would be breathing at less than 20, and it's certainly not a rapid respiratory rate, no.

NELSON: How about certain types of phobias?

FOWLER: Yes. If you have a phobia and you are pushed into a situation where you have to face a phobia, it's stressful and it will fire up your fight or flight type of situation.

NELSON: And how would that affect the respiratory rate?

FOWLER: Well, the moment you go to fight or flight and your adrenaline is surging, you are likely to start -- some people hyperventilate, there are lots of variables there.

NELSON: So, again, in terms of the respiration rate, you would expect it to increase well beyond the normal rate?

FOWLER: Yes, I would not expect it to slow down.

NELSON: Okay. In terms of the placement of the knee and the neck, could you determine, based on your review, whether it appears his airway was obstructed?

FOWLER: Yes, the placement of the knee is towards the back and the back right side of Mr. Floyd's neck, and the airway is around the front. It is nowhere close to his airway. NELSON: We're talking about having an open airway. How does that affect your ability to speak?

FOWLER: The ability to speak or make any other sound, groaning, and Mr. Floyd did grunt, so any of the sounds that Mr. Floyd is making requires you to be able take it in over the vocal cords and out over the vocal cords. And so, therefore, you cannot make sound unless you are moving air and your mouth is open and people can hear to some extent. I can hum with my mouth closed but I'm not (INAUDIBLE).

The bottom line is moving air in and out is -- and speaking and making noise is very good evidence that the airway was not closed.

NELSON: Now, in terms of, again, prior testimony, did you review or watch the testimony of Dr. Tobin?

FOWLER: I did not watch all of his Dr. Tobin's testimony, no.

NELSON: Did you hear him discuss the hypopharynx?

FOWLER: I did.

NELSON: And hypopharynx compression?


NELSON: Have you ever seen anything in the forensic medical literature that a compression of the hypopharynx can cause asphyxia?

FOWLER: I have not.

NELSON: When you heard his testimony, what steps and efforts did you take to consider that?

FOWLER: Started to do a survey of the available medical literature to ensure that I hadn't missed something. And I could not find --

UNIDENTIFIED MALE: Objection, your honor. Sidebar.


FOWLER: I could not find anything in the forensic literature talking about pressure applied to the neck causing a hypopharynx --

UNIDENTIFIED MALE: Objection, your honor. (INAUDIBLE).

CAHILL: Overruled.

FOWLER: And then I went to the standard medical literature, and there are entities which cause impaired little (ph) hypopharynx, but they are usually -- theye all were focused on foreign bodies being inhaled, such as hot dogs or some another object, and then also tumors in that area potentially blocking of that structure, so nothing that really matched the testimony of Dr. Tobin, as I understand it.

NELSON: In terms of hypoxia, moving back to the hypoxia, is hypoxia -- the signs of hypoxia, is that a progressive or a fast process?

FOWLER: Typically, it can be both, but you have to recognize that there is oxygen in your blood that is there and it takes a while to use up that particular oxygen. So, in most circumstances, the onset of hypoxia is gradual. If I restrict somebody's breathing and slow it down by some means or stop it by some means, there is still oxygen dissolved in their blood.

You can hold your breath at 30 seconds with comfort, and 45 seconds you are probably getting uncomfortable and want to breathe, and that's your inmate reflex trying to override your voluntary suppression of your breathing. And you could go for a minute before start to feeling woozy and/or uncomfortably and disoriented.

And so that's the heart continuing to distribute what you have got in your body. So we see hypoxia occurring gradually in most circumstance over time. It's not something which is a on and off switch and rapid.

NELSON: And as far as the symptoms that you see or would expect to see in a hypoxic situation, do they gradually progress like that as well?

FOWLER: Typically, yes.

NELSON: Did you notice hypoxic changes in this particular case?

FOWLER: No. Mr. Floyd was coherent and understandable until shortly before there was a sudden cessation of his movement.

NELSON: So if Mr. Floyd, in this case, was progressively suffering from hypoxia, what would you have expected to observe?

FOWLER: I would expect him to become disoriented, confused, incoherent.


I would expect some of those symptoms to be at least somewhat apparent.

NELSON: And you would have -- would your review -- in your review of the videos, would you have expected to see a progression in that hypoxia?

UNIDENTIFIED MALE: Objection, your honor, asked and answered that clinically --

NELSON: Sorry, I --

CAHILL: Sustained.

NELSON: Understood. Now, how about asphyxia due to position or compression, let's talk about that. What is that effect?

FOWLER: So there are certain positions a person can get into which impairs your breathing. NELSON: And does that -- what does that lead to?

FOWLER: It leads to difficulty in moving your diaphragm and your chest and impairing your ability to re-oxygenate your blood.

NELSON: Can that lead to hypoxia?


NELSON: Which bodily organ would you expect to see affected first?

FOWLER: The brain.

NELSON: And all of those affects on speech and orientation and things progressing?

FOWLER: Correct.

NELSON: You describe what you saw as a sudden change, what does that mean to your analysis?

FOWLER: So, Mr. Floyd goes from making clear statements, and some of the words I heard were please, I'm short of breath, please. And then there's a period of about 45 seconds of silence, but he's still moving. And he seems to be active, and then there's a sudden relaxation. And so he goes from pretty much fully functional and coherent to unconscious very rapidly.

NELSON: So in this particular case, how does his 90 percent blockage of the right coronary artery come into play?

FOWLER: So what you are looking at there is a sudden de*compensation, which is much more consistent with a sudden cardiac event. And what happens there is the moment the heart stops pumping sufficient blood, there is no circulation of blood. There is no circulation of the blood that still some oxygen in it. And the brain will function for about 15 seconds, 10 to 15 seconds with full consciousness.

After that, the person loses consciousness but it's not instantly that -- people don't suddenly stop breathing when they go unconscious. They will continue to breathe for a period of time, which can be as long as a minute or two, until the respiratory center in your brain shuts down. And at that stage, the person stops breathing.

NELSON: So in this case, can you just kind of describe the layers of factors that lead you to your conclusion that this was a sudden cardiac event?

FOWLER: Yes. So we have a heart that is vulnerable because it's too big, it demands lots of oxygen, it has very narrow vessels. There are certain drugs that are present in his system that make it -- put it at risk of any arrhythmia, the methamphetamine. There is another drug, fentanyl, which slows down your breathing, which would lower the oxygen potentially saturation in your blood. We've got the carbon monoxide, which has a potential to rob some of the additional oxygen- carrying capacity. And then we've got vasoconstriction. So there are multiple entities all acting together and adding to each other and taking away from a different part of the ability to get oxygen to his heart. And so at some point, the heart exhausted its reserves of metabolic supply and wait (ph) into an arrhythmia and then stop pumping blood effectively.

NELSON: Now, just a couple more topics to just cover with you, Doctor. You did review the -- well, in any death investigation, do you review the role that controlled substances play in death?



NELSON: Do you do that on a regular basis?

FOWLER: It's a very important part of a forensic investigation. And most medical examiner's officers will try to get close to 100 percent toxicology analysis on their cases if supple specimens are available.

NELSON: Now, in terms of the toxicology in this case, how would you characterize the role of fentanyl from the standpoint of forensic pathology, not toxicology, forensic pathology?

FOWLER: So, fentanyl is a powerful narcotic. It's about 80 times more powerful than morphine. And the side effects of fentanyl are slowing down the respiration. So that impairs your ability to breath as fast as you normally would.

NELSON: Does that result in increased -- or, excuse me, decreased oxygen saturation?

FOWLER: It would result in decreased air exchange, which would mean decreasing the oxygen in the bloodstream but also not fully getting rid of the carbon dioxide, the byproducts around normal metabolism. So it's slowly increasing carbon dioxide in his blood stream.

NELSON: Now, again, within the context of forensic pathology, what is the presence of norfentanyl mean to you?

FOWLER: Norfentanyl is a by-product of fentanyl. It's a metabolic byproduct. And so in your liver, or in Mr. Floyd's liver, as the fentanyl pass through the liver, it was broken down into norfentanyl, which is the metabolic byproduct. It's the liver beginning to destroy and metabolize the fentanyl and remove it from the body's system.

NELSON: Now, I'm going to -- for the court I have -- there are three slides contained within your Powerpoint presentation. I have independently marked them as Exhibits 1059, 1060 and 1061. I would like to show them to the witness.

Can you see that, doctor?


NELSON: Would you agree that this appears to be a screenshot taken from a body-worn camera of Officer Lane at 20:09:44?

FOWLER: Correct.

NELSON: Looking at the second one, would you agree that this, again, appears to be a body-worn camera image taken at 20:09:45?


NELSON: And, finally, a third image at 20:09:48?


NELSON: All right. I would offer 2059, 2060 and 2061.

UNIDENTIFIED MALE: No objection, your honor.

CAHILL: They are received.

NELSON: And permission to publish 1059.

And so in this, Doctor, it's kind of hard to see, what, in your review, did you determine whether there was the possibility that controlled substances were ingested at the time of approach by Officers King and Lane?


NELSON: And what do you see in this image, 1059, that is consistent with that?

FOWLER: In the back corner of Mr. Floyd's mouth, you can see what appears to be a white object.

NELSON: Are you talking this object right there?

FOWLER: Just slightly higher up that, yes.

NELSON: I can't -- why don't you do it?

FOWLER: Sorry, I can't lift the dot but that's what I am referring to.

NELSON: All right.

FOWLER: It's just underneath the dot.

NELSON: Now, in the next image, 1060, what appears to be happening?

FOWLER: In this particular image, it appears that Mr. Floyd is looking away -- excuse me -- from Officer Lane.

NELSON: And looking at the timestamps, that's approximately one second later?


NELSON: And in the third image, does he appear to be looking at Officer Lane again?



NELSON: And do you see that same object in his mouth?

FOWLER: I can, yes.

NELSON: You can. And so what does this lead you to conclude or what do you -- strike that. Oops. In terms of the later analysis, you understand there was evidence collected from the backseat of Squad 320?

FOWLER: That is my understanding, yes.

NELSON: And do you know what that substance was?

FOWLER: The -- there was some material there that had saliva and DNA on it that matched Mr. Floyd and those, I believe, objects had fentanyl and methamphetamine, if my memory serves me correctly.

NELSON: So, is that what your conclude your analysis on in terms of the ingestion of the controlled substances as far as the timing in this case, before they were approached as well as during -- in the back of the squad car?


NELSON: Now, how does the depression of the respiratory rate -- we may have covered this, I apologize. How does the depression of the respiratory system, how does that affect the heart?

FOWLER: If the respiratory rate is decreased, the amount of oxygen that is getting into the bloodstream through the lungs is decreased. If I breathe slowly, I'm not able to get as much oxygen into my lungs as if I am breathing very rapidly. So anything that slows down respiration is going to affect the ability to oxygenate your blood.

NELSON: And would that work in concert with the coronary artery issues?

FOWLER: It makes it worse. Again, anything which lowers his oxygen saturation in the blood will act, begin to restrict oxygen supply to his heart muscles post that (INAUDIBLE).

NELSON: How about the -- you also understand that methamphetamine was found in the toxicology?


NELSON: And how would you look at the role of methamphetamine from the perspective of a forensic pathologists?

FOWLER: So, methamphetamine has three major factors. It can cause arrhythmias, it causes vasoconstriction and it causes the heart to beat faster. Those are its three major physiological or pharmacological activities. And that would impair, again, an individual in Mr. Floyd's condition with his heart disease and put him at risk.

NELSON: Now, in terms of, again, the toxicology findings, in the fentanyl, there was the metabolize norfentanyl, correct?


NELSON: What does that tell you in terms of the timing of when Mr. Floyd may have ingested the fentanyl?

FOWLER: It tells some of the fentanyl was taken at some point previous -- sometime before that allowed for enough time for the fentanyl to be absorbed and then passed through the liver and some of it to be broken down. That doesn't happen instantaneously, it can take a period of time.

NELSON: And methamphetamine, does it have a similar metabolite?

FOWLER: It a metabolite, yes.

NELSON: And what is the metabolite?

FOWLER: Amphetamine.

NELSON: And based on your review of the toxicology in the case, was there amphetamine found?

FOWLER: I did not see any amphetamine in the reports.

NELSON: What does that suggest to you as a forensic pathologist relevant to the time which Mr. Floyd would have ingested that methamphetamine?

FOWLER: So that would be consistent with a recent ingestion of methamphetamine.

NELSON: And in terms of the phase of absorption or elimination, where would that place him?

FOWLER: Well, if there is no evidence of elimination, i.e., metabolism from methamphetamine to amphetamine, it's not in the elimination phase. And given there appears to be -- it's probably be in the absorptive phase. It's consistent with the absorptive phase?

NELSON: And, ultimately, those pills that were found in the backseat of the squad car, you understand that when Mr. Floyd was in the squad car, he was handcuffed.



CAHILL: Rephrase. Sustained.

NELSON: What information did you have about Mr. Floyd's ability to ingest those controlled substances while he was in the squad car?

FOWLER: He had his hands cuffed behind his back from the videos, and those were placed outside when he was taken out of his own vehicle. I did not see any time when those were removed until such time as resuscitation was (INAUDIBLE). So, the entire time, he had his hands cuffed behind his back, and, therefore, I cannot think of a plausible way that an individual would be able to get materials into their mouth while restrained in such a format.

NELSON: Now, the last topic I would like to discuss with you is the paraganglioma. Did I say that right?

FOWLER: That is close.

NELSON: All right. Can you just describe what that is?

FOWLER: Paraganglioma, so this is a tumor that was found at the time of autopsy down in Mr. Floyd's lower be abdominal area. And these are tumors and they typically are of two types, one which is -- has parasympathetic or is similar to the parasympathetic part of your nervous system, which does not secrete any substances or certainly vasoactive substances ,like catecholamine, and then there are the sympathetic ones which have the ability to secrete.

The parasympathetic ones tend to be found at the head and neck area, and the sympathetic ones tend to be found down in the lower abdominal area. Again, this was Mr. Floyd's was found.

NELSON: What's the relevance of finding the paraganglioma in this case?

FOWLER: So these tumors have -- at least the ones in the pelvic area, if they are secreting vasoactive substances, catecholamines is the correct term, they will cause an individual potentially to be hypertensive. So that's one of the their baseline, if they had a low level of secretion.

And the other thing that paragangliomas do is, every now and then, without a warning, they will have a sudden surge in secretion, so they're cyclical, which sometimes makes it difficult to diagnose them. You have to do specific testing to diagnose them to get around the cyclical activity.

NELSON: So, just kind of in conclusion, Doctor, did you form ultimately opinions as to the cause and manner of death of Mr. Floyd?


NELSON: And what would those conclusions be?

FOWLER: Mr. Floyd died of a cardiac arrhythmia due to hypertensive atherosclerotic cardiovascular disease during the restraint.

NELSON: And were there contributing causes?

FOWLER Yes. NELSON: What are those?

FOWLER: the substances, the fentanyl and the methamphetamine, the potential of a carbon monoxide role and the potential of the paraganglioma was adding adrenaline to this whole mixture making things even worse.

NELSON: How would you classify the manner of death?

FOWLER: So this is one of those cases where you have so many conflicting, different manners (ph). The carbon monoxide would usually be classified as an accident, although somebody was holding him there. So, some people would say you could elevate that to a homicide.

You've got the drugs onboard. In most circumstances, in most jurisdictions, a drug intoxication would be considered to be an accident. He's got significant natural disease, certainly the heart. The paraganglioma, you can certainly consider it as a potential exacerbating process, but I wouldn't put it on top of the list there. So he's got a mixture of that.


And then he's in a situation where he has been restrained in a very stressful situation.