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Defense Questions Pathology Expert in Chauvin Trial. Aired 11:30a-12p ET

Aired April 14, 2021 - 11:30   ET


ERIC NELSON, DEFENSE ATTORNEY: Necrosis and how -- whether that's necessary to diagnosis a sudden cardiac death?


DR. DAVID FOWLER, FORMER CHIEF MEDICAL EXAMINER, MARYLAND DEPARTMENT OF HEALTH: Myocyte necrosis is both something you can -- you have to visualize it microscopically. You have to look at the individual heart cell. The myocyte is just a word which is heart cell. You can infer that there may be some myocyte necrosis at autopsy if you see bleeding into the heart itself, but it is a microscopic diagnosis. And it is not necessary for myocyte necrosis to be present for a sudden cardiac death.

NELSON: So, someone who has a sudden cardiac death may not have myocyte necrosis?

FOWLER: Correct.

NELSON: Why might that happen? Why might someone not have that myocyte necrosis?

FOWLER: Again, the heart goes through a process of dying. It takes a while for a heart to die and for the actual myocytes to start showing the changes that we can see under the microscope. And we need to understand that that's why you can do heart transplants.

When somebody who has been injured or suffered some other catastrophe to their brain and is brain dead and is a donor, their heart can be removed, put on ice, flown across the country and put into another person without any damage to that heart. That process takes hours.

So if the death is rapid, you will not see myocyte necrosis. It's the timeframe from the heart stopping. The time we typically see myocite necrosis is going to be somebody who has had symptoms and survived for a period of time so that process can advance to the degree where we can see it under the microscope.

NELSON: Now, you've kind of talk about sudden cardiac events. Let's talk about the arrhythmia. Can you describe what is called the conduction system of the heart?

FOWLER: The conduction system of the heart is a very important part of the orderly contraction of our heart. We have two chambers which receive blood from the body, the atria, and then we have two bigger, very muscular chambers, the ventricles, that pump blood under high pressure to the body.

And so the way the heart works, it's a two-chamber on each side, one side supplying the lungs and the other side supplying the body, where the atria contract and push blood into the ventricles to fill them up. And then the ventricles contract to push blood to the body. The ventricles are very powerful, and there's a valve in between them to stop the blood from flowing back.

So, what you need is an orderly contraction process where the atria contract first followed by the ventricles. This is coordinated by the conduction system. And we have in the heart what is known as the cardiac pacemaker, it's a generic term, but it's the little piece of modified heart muscle that actually has almost nerve-like function.

NELSON: Does that have a name?

FOWLER: It's called a sinoatrial node. And that generates the initial activity which causes the atria to start contracting, and between it and another node which is at the junction of the atria and the ventricles, called the atrioventricular node, there is a little bundle of modified heart muscles that conduct that down. And then there are further modified heart muscles that go down to spread the impulse, the electrical impulse to the heart to cause it to contract.

NELSON: What are those called?

FOWLER: That's -- it's the bundle of (INAUDIBLE), fibers, et cetera, they all have medical terminology. But, basically, it's modified heart muscle cells.

What that does, is the sinoatrial node fires, the impulses conduct down and fires to the A.V. node. And at that time the atria contract, forcing the blood. At the time that the impulse arrives at the ventricle, that nerve then fires shortly after the atria and the heart contracts and sends the blood on its way.


So you get this orderly double beat to the heart. You can hear the valves opening and closing, atria first and then the ventricles. And that's the sounds that the physicians listens to when he puts a stethoscope over your heart.

NELSON: That's the blood pressure?

FOWLER: Sorry?

NELSON: Is that blood pressure or --

FOWLER: So, the blood pressure is actually generated by the contraction of the ventricles. That's the essential output of the heart, is directly related to the volume and pressure of blood that is pushed out of the heart.

NELSON: Okay. So what happens if this conduction system gets impaired?

FOWLER: Then you don't have orderly contraction of the heart. And so if they fire at the wrong time, then -- if you had the atria and ventricles firing at the same time, you would move no blood.

The ventricles are very powerful. They slam that valve shut. The atria fire at the same time. They can't force blood past it, and so you've got no flow to fill the ventricles.

NELSON: And is that an arrhythmia?

FOWLER: That's an arrhythmia. There are multiple different types of arrhythmia that are documented.

NELSON: And what can happen -- can sudden death happen as a result of an arrhythmia?

FOWLER: Absolutely.

NELSON: So, which artery supplies that pacemaker, the S.A. node that you described?

FOWLER: The sinoatrial node is supplied by a small branch that comes off the right coronary artery.

NELSON: And did you review, again, the autopsy and observe findings relevant to Mr. Floyd's right coronary artery?

FOWLER: Yes. So, unfortunately, that was the artery which showed the greatest degree of narrowing.

NELSON: Which was how much?

FOWLER: 90 percent.

NELSON: Does that increase or that type of narrowing increase the risk for sudden death?

FOWLER: Yes, in that if and when the blood supply needs of the heart on the right side increase -- and that's also going to apply to the sinoatrial node -- are not met, that sinoatrial node will not function properly, and will not fire properly. And you will end up with an arrhythmia of some sort.

NELSON: So, essentially, if it misfires, there's no pacemaker?

FOWLER: That is correct, yes.

NELSON: How does exertion come into the analysis?

FOWLER: Exertion basically increases the demand for oxygen throughout the entire body, mostly because of the muscular activity. So, as we exercise, our heart rate and our breathing rate normally compensate to increase the oxygen that we're bringing into the body through the respiratory system and increase the amount of blood or amount oxygenated blood, which is being distributed to the body. And the way that increase of blood -- the way the body increases the blood supply is to increase the rate of the heart. So we will go from our resting heart rate, which is somewhere between 60 and 100. We'll push it up to 120, 140, 150, depending on the degree of exertion, and beyond it gets dangerous.

NELSON: So, essentially, the more exertion, the more oxygenated blood is needed?


NELSON: How do drugs like methamphetamine come into play as far as the -- in terms of the conduction system?

FOWLER: So, methamphetamine is dangerous at several levels in this particular case. One, it has known arrhythmogenic potential. In other words, it sensitizes the heart to arrhythmias. It's been documented that people on methamphetamine have an increased risk of an arrhythmia.

Secondly, it increases the rate that the heartbeats. As a stimulant, it pushes the heartbeat rate up. So, therefore, the heart is now going to demand increased oxygen, the heart muscle itself.

And, thirdly, it is a vasoconstrictor.

NELSON: What is a vasoconstrictor?

FOWLER: So, a vasoconstrictor is a substance that causes blood vessels and arteries to narrow. And it's physiologically important and it is particularly in certain circumstances but can become dangerous in others.


And the way that the vasoconstrictor works in most circumstances is to act on the muscular layer that's present in arteries. Now, arteries have multiple different layers, and there's a muscular layer in there, and it causes that muscular layer to begin to contract. A little bit of contraction is good. Too much contraction, and it can slow down the blood beyond what is necessary, and even in certain circumstances you can stop the blood by giving a vasoconstrictor substance.

NELSON: So in this particular case, we have got an enlarged heart, right?


NELSON: We have a heart that has narrowed coronary arteries, right?


NELSON: And based on your review of the video evidence, you observed a pretty significant struggle between Mr. Floyd and the three officers?

FOWLER: Correct.

NELSON: Methamphetamine on board, which is a vasoconstrictor?


NELSON: Have you or your colleagues ever certified a death due to the atherosclerotic coronary artery disease?

FOWLER: Yes. It's a very unfortunately and very common cause of death.

NELSON: And even at these levels of narrowing of 75 to 90?

FOWLER: Anything above 75 percent, as I previously mentioned, meets the criteria for enough narrowing, at least within the community of practice of forensic pathologists.

NELSON: Have you ever performed an autopsy sort of expecting one cause of death and finding another?

FOWLER: That's why we perform autopsies. It's a thorough internal examination to identify anatomic deviations from normal. And so, therefore, your preconceived notion -- I wouldn't say a common example, but we see it every now and then, would be a motor vehicle collision, where somebody has multiple injuries, and you look at them and go, okay, they've got enough injury there to kill them. But when you go in, you can see evidence that they had a stroke or a heart attack. And that's what potentially caused them to lose control of their vehicle at the time that they had and got their multiple injuries.

And so then we stick with the issue of do we put the heart attack under part one or do we put the heart attack and/or stroke-type findings under significant conditions, because, obviously, they were driving their vehicle, but it may have caused them to lose consciousness. And so these are just dilemmas that we face as to where you put things on the certificate, and not sometimes you're not right and you're not wrong.

NELSON: How about hypertensive cardiovascular disease? How does that relate to a cause of death?

FOWLER: So, again, there are a number of sudden cardiac deaths that are related solely and exclusively to the increased size of the heart. And so those are the ones that, since hypertensive disease is the most common cause of an enlarged heart, we will typically use that as the cause of death and say hypertensive cardiovascular disease.

NELSON: Have you ever certified a death due to hypertensive cardiovascular disease?

FOWLER: Yes, I have, multiple times.

NELSON: Have you diagnosed both hypertension and coronary artery disease as a cause of death in combination? FOWLER: Yes, and, again, that is probably even more common because a significant portion of the population have hypertension, so their hearts are enlarged. And as you get older, you tend to lay down deposited material in your arteries. Also there' often both are present in many, many cases, unfortunately.

NELSON: Now, again, in terms of hypertensive cardiovascular disease, we talked earlier about the struggle between Mr. Floyd and the officers getting into the squad car. How does that type of exertion play into hypertensive cardiovascular diseases?

FOWLER: It increases both the hypertensive and the (INAUDIBLE). It increases the demand and the stress on the heart. And the more the individual is stressed, both physically and in other ways, the more the demand on the heart is going to increase.


NELSON: So, in terms of stress, how does that affect the heart?

FOWLER: So, we have certain innate stress mechanisms built into us, reflexes built into us. It's called the fight and flight reflex is the common terminology that you'll see within the medical literature and also within the lay literature. And this is a mechanism where, if you are in a stressful situation, it prepares your body to be able to cope with the stressful situation.

And what happens generally is the sympathetic part of your nervous system begins to act. That causes secretion of adrenaline, as one of the example and perhaps or other catecholamines, which are substances that are part of that sympathetic nervous system, and adrenaline causes your -- some of your blood vessels to constrict. It's another important vasoconstrictor, the idea being that you don't need to digest the food in your stomach, for instance, while you're in a very, very dangerous environment. So it really shunts the blood, pushes the blood to the organs that are more important, the heart, the lungs, the brain, your muscles. And it also shuts down the blood supply to your skin. And so it does all of those things.

But it also speeds up the heart to increase the cardiac output to maintain oxygenation of the brain, your muscles and other things so that you can have an additional reserve to fight that threat.

NELSON: All right. So, the flight or fight that you described, it increases adrenaline, right? It causes the heart to beat faster, agreed?

FOWLER: Yes, and yes.

NELSON: And the adrenaline -- how does that come into play? Did you say that was a vasoconstrictor?

FOWLER: Adrenaline is a vasoconstrictor, yes.

NELSON: And including the arteries?

FOWLER: Oh, yes.

NELSON: And, ultimately, what does that do potentially?

FOWLER: So it narrows the arteries. And, again, we have smooth muscle in the cardiac arteries. So there's a potential of the adrenaline and the methamphetamine further narrowing those arteries in the heart as well as arteries elsewhere in the body, restricting blood flow.

NELSON: Now, in terms of that kind of stress reaction, I would like to craft this question carefully, the jury saw some evidence, which I know you reviewed as well, of an incident in 2019, about a year prior to Mr. Floyd's death, where Mr. Floyd was stopped by the police, was seen -- believed or admitted to ingesting some controlled substances at that point and was subsequently seen by paramedics. Do you recall that information in the information you reviewed generally?


NELSON: And at the time that he was initially seen by paramedics, he -- his blood pressure was taken, and if I'm not mistaken, it was 216 over 160. What does that signify to you as far as this stress relation?

FOWLER: So, a high blood pressure like that, and that's markedly elevated, could be due to his hypertension being out of control. But this is much higher than I would expect.

Secondly, it could be part of the stress reaction where adrenaline is being secreted and it's pushing his heart rate up, and that will increase your blood pressure. And if adrenaline is secreted, it's also causing vasoconstriction, so there's more blood in the central vasculature, and so, therefore, that will increase your blood pressure.

There are multiple explanations for that. And certainly stress would be one of them.

NELSON: Your honor, I believe that will be a good time for our mid- morning break.

UNIDENTIFIED MALE: (INAUDIBLE) reconvene at 11:10.

KATE BOLDUAN, CNN NEWSROOM: Hello, everyone, Kate Bolduan here. We have been watching the first of the second day of the defense team presenting their case in the murder trial of Derek Chauvin.

Let me bring in CNN Legal Analyst Laura Coates, as well as Cedric Alexander, former President of the National Organization of Black Law Enforcement Executives.


Laura, you have been watching this throughout the morning along with me. And what is your reaction from what we have learned from this defense expert? LAURA COATES, CNN SENIOR LEGAL ANALYST: You know, I am starting to question the expertise. I understand that there could be other causal factors. It's part of what this case is about, like the heart of the matter. But now, to have this expert suggest that carbon monoxide poisoning and having George Floyd's face near the exhaust pipe may have been an equal contributing factor to a knee on the neck.

And at that point, we're more than an hour into this person's testimony and we have not yet heard this expert address the use of force or the physical restraint by Derek Chauvin for a sustained period of time, and instead he's said it was a sudden death? I am unclear as to what nine minutes 29 seconds worth of sustained use of force after someone is no longer conscious could mean about being sudden.

And, finally, just compare, if you will, Kate. You've been watching. You've watched last week. Compare, set aside the facts of the case just for a moment and compare the defense versus prosecution experts. Which one informed you, which one clarified, which one confounded or confused, who spoke plainly, who invited more speculation? This is part of what the jury is going to be grappling with to bring out the credibility and who to believe.

BOLDUAN: And, Laura, you are getting exactly what I was going to follow-up on, is the experts here are in conflict. And that is not new in a trial though. Both the prosecution and the defense, they bring their witnesses, they bring their experts forward. How are juries, I don't know, instructed or how do juries grapple with this? Do you think the fact that let's just be plain-spoken here, this expert, the way he's talking about and going through things, it is more confusing than the experts we heard previously from the state's case. Is that a strategy? Is that a goal?

COATES: It's not a goal for the defense. It's a goal for the prosecution to have the superior witnesses to be who were able to use demonstrative. Remember, we were following along with that pulmonologist when he told people to touch their neck in certain areas. Remember, the defense had to object and say, your honor, please tell the jury they aren't required to actually follow along. And even when the judge said that, they still did so. It was bite-sized pieces, it was digestible.

And you want that sort of flow because you want the jurors, who are the ones who are going to actually decide this case to have as much information as possible to feel as informed as the armchair pulmonologist or cardiologist, and say, I have enough information now to decide. And what you are having with the witness is this meandering around other grasping of straws, and saying, well, it could have been this, or perhaps maybe he might go at some point and say, Kate, maybe there was a reaction to some chemical in the pavement and that could have been a reason that George Floyd died.

Unless they address the real elephant in the room which is use of force as it related to George Floyd's neck and his body and respiration, unless they get to that and address this point, you really fatally undermine your credibility and do a disservice to your expert.

BOLDUAN: It is about introducing doubt, introducing another theory, a could, a maybe. And we see that today, Cedric. We also saw that yesterday when the defense brought forward especially one former police officer who made the argument, this was a defense expert on use of force, that he thought that the officers could have even used more force from what he saw in the videos. What is your thought on this?

CEDRIC ALEXANDER, CNN LAW ENFORCEMENT ANALYST: Well, you know, the defense, what they presented on yesterday was a witness, a defense witness, quite frankly, did not go at the heart of the matter but spoke in a way in which a great deal of uncertainty from what I could gather from him. But that was his job, that was his role as a defense witness. But there's really nothing very concrete or scientific about anything that he stated.

So we look at this witness today, a scientist, one that has a great deal of credibility, that has been established. But it goes back to this in all of this. If you look at -- and I was a police officer out on those streets, and certainly you will come in contact with people that you may have to get physical with, in which you don't know their health condition. None of us do.

We know that there's a significant number of people in our population across this country that suffer with heart disease, et cetera, et cetera. But when you have someone in your custody, you have them handcuffed, you have them against a hard surface, they are telling you they cannot breathe, and everything that you are doing is that you are compressing further that they don't breathe, I don't know how that can overwhelm what we are hearing this morning and what we heard yesterday morning.


Because to me, as a layperson in the mind of those jurors, they're going to see this in a very basic and fundamental kind of way. You can throw all the technical scientific language that you want, all you want to, but even in Dr. Tobin, who was so precise, so articulate, so fundamental in helping people understand the basic science of what took place and how George Floyd suffered was a significant presentation. And I haven't seen anything that has gone beyond that because all I'm just seeing too for the last couple of days, trying to object that had been fair (ph) and listening like this but what you're hearing is not something, anything that is substantive that is going to -- I think is going to make any difference to your jury.

BOLDUAN: They are in a quick break now. They're in a morning break. The defense will be picking back up with witness testimony and questioning very shortly and we're going to take you back to Minneapolis. We'll be right back.