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

Aired April 14, 2021 - 11:00   ET




The microscopic examination, which the pathologist will do themselves, it takes a while for the glass slides. So, some cases can take two to three months.

NAME actually has a requirement that you should complete 90 percent of your cases within 90 days. Otherwise, you cannot be accredited. They prefer you to do it within 60 days. But 90 percent of cases should be completed within 90 days. That's three months.

And the 10 percent of cases that aren't completed are going to be very complex cases. Often the deaths in custody and the pediatric sudden deaths are the ones that fall into that 10 percent. They often go on even further as you gather all that information.


So can you explain what the death certificate is? Ultimately a death certificate is issued, right?

FOWLER: Correct.

NELSON: And can you explain what the death certificate is?

FOWLER: So, the death certificate is a document produced by a physician. The greater majority of them are signed out by physicians within the hospital or nursing home, et cetera, medical examiners are usually exposed to about 25 percent of deaths within their jurisdiction. So, the death certificate is a certification that the person has died and within a reasonable degree of medical certainty, the certifying physician believes that whatever is on the cause of death line is the cause of death within a reasonable degree of medical certainty.

NELSON: So let me ask you, in terms of this particular case, you've reviewed a substantial amount of information?


NELSON: Can you just briefly describe the information you've reviewed in this case?

FOWLER: Gosh, it goes on for several pages, but there are past medical records, the records that occurred at the hospital at or about the attempted resuscitation occurred. There are ambulance records, police records, toxicology information. There are multiple videos from multiple sources, body-worn cameras, surveillance videos from stores and other facilities in that area.

There was video material from observers that is available. There's the toxicological data. There's the autopsy information, the autopsy photographs, the microscopic examination. It goes on and on and on. There's a substantial amount of information on this case.

NELSON: And before we kind of get back to the death certificate in this particular case, upon your review an based on your training and education, your experience as a forensic pathologist, have you formed opinions in this case to a reasonable degree of medical certainty?


NELSON: We'll come back to those shortly.

So in terms of the death certificate, are there two parts to that?


NELSON: And can you explain those two parts?

FOWLER: So, the first part is what the physician believes to be the cause of death. So that is something that you will put -- what we called part one. That's what the CDC refers to it. The death certification process is one which is controlled and governed by the CDC, although each state will have a slightly different format to their death certificate and the way they do things. The guidelines that are put out there by the CDC for completion of their certification are certainly ones that are national.

NELSON: So what's the first part of the death certification according to the CDC?

FOWLER: The first part is the primary cause of death.

NELSON: And what's the second part, per the CDC?

FOWLER: Are there significant things contributing to death but not directly related to what's in part one.

NELSON: Now I'm going to ask -- I'd like to show exhibit 193 which is already in evidence. Do you see that in front of you? And I ask to publish.

You're familiar with this document?

FOWLER: I have seen this document, yes.

NELSON: And what is the first part of the certification of death? FOWLER: So, the first part, the causes of death is cardiopulmonary

arrest complicating law enforcement subdual restraint and neck compression.


NELSON: Now, under that, there is the phrase saying underlying. Is that what you're referring to in terms the of the second part per the CDC?

FOWLER: No. The way the CDC normally phrases it is you can break it out into multiple lines. It could be cardiac arrhythmia due to such and such, due to such and such. So that's where the underlying conditions come into the death certificate. At least when you look at the CDC guidelines and the death certificates that I'm used to completing.

The second part that I referred to as part two, on this death certificate is called other contributing conditions.

NELSON: And what are the other contributing conditions that you reviewed here?

FOWLER: So on this particular death certificate, the certification says that atherosclerotic and hypertensive heart disease, fentanyl intoxication and recent methamphetamine use are considered contributing conditions.

NELSON: So this was prepared by Dr. Baker, correct?

FOWLER: Yes, that is my understanding, that he was the individual who certified this case.

NELSON: So in terms of Dr. Baker's analysis of this case, how did the heart and drugs contribute to the cause of death?

FOWLER: They were significant -- they contributed to Mr. Floyd having a sudden cardiac arrest in my opinion. That's how I would read it.

NELSON: Okay. We're going to get take this one -- if we can unpublish, all right.

Doctor, did you prepare a PowerPoint presentation to walk through your opinions in this case?


NELSON: Judge, I identified this as demonstrative exhibit 1098, and I'd move to publish.

JUDGE PETER CAHILL, HENNEPIN COUNTY COURTHOUSE: Any objection to 1098 for demonstrative purposes only?

UNIDENTIFIED MALE: No, your honor.

CAHILL: All right. This is received for that purpose alone. NELSON: So, before we begin, Doctor, can you summarize briefly what

your opinions are in this case?

FOWLER: Yes. So in my opinion, Mr. Floyd had a sudden cardiac arrhythmia or cardiac arrhythmia due to his atherosclerotic or hypertensive disease, or you can write that down multiple different ways, during his restraint and subdual by police or restraint by the police.

And then his significant contributory conditions would be, since I already put the heart disease in part one, he would have the toxicology, the fentanyl and methamphetamine. There is exposure to a vehicle exhaust, so potentially carbon monoxide poisoning or at least an effect from increased carbon monoxide in his bloodstream and paraganglioma (ph), or the other natural disease process that he has.

So, all of those combined to cause Mr. Floyd's death.

NELSON: All right. So let's walk through each of these if we could, starting with the opinions of Dr. Baker as far as the cardiopulmonary arrest.

Before we do that, if we could publish the exhibit, Your Honor.

Can you just describe what -- what this is and why it's relevant to this case?

FOWLER: So this is a document that is produced as a guide for medical examiners to use when certifying the death, and specifically the manner of death.

NELSON: What is the manner of death?

FOWLER: So, the manner of death is how did the cause of death come about. And you have five different choices that you can check off for write down on a death certificate as to the manner of death.

NELSON: Now, does this document specifically address as asphyxial death, positional asphyxial deaths?


FOWLER: It addresses all sorts of manner of death, and again, it's a guideline put out to assist medical examiners. And, unfortunately, not every case cleanly fits into one particular category or meets the criteria for the guidelines.

NELSON: OK. So let's talk about in terms of this second slide. Positional restraint. How does NAME deal with autopsies and death investigations involving positional restraint?

FOWLER: So, the recommendation is that what's a recommendation? They say you may be classified as a homicide.


FOWLER: It doesn't say shall or should. It says may be classified as a homicide.

Again, we have to recognize that these are medical guidelines. And it then goes on, and everybody I think can actually easily read that, if you want to go back one.


FOWLER: IIn such cases there may not be intent to kill, but death results from one or more intentional, volitional, potentially harmful acts directed at the decedent, without consent, of course. Further, there is some value to the homicide classification toward reducing the public perception that a cover-up is being perpetrated by the death investigation agency.

NELSON: Now, in terms of the five manners of death that you described, again, we've heard testimony or the jury has heard testimony from other experts who have testified. There's homicide is one, suicide. Can you describe the others?

FOWLER: So, homicide, suicide, accident, natural and then undetermined.

NELSON: So, this next slide, can you describe what undetermined means according to the guidelines?

FOWLER: So, according to the guidelines, undetermined, or the other term on some death certificates is "could not be determined" is a classification used when the information pointing to one manner of death is no more come compelling than one or more other competing manners of death in thorough consideration of all available information.

NELSON: And the guidelines also define homicide?

FOWLER: Yes. And again, homicide occurs when a death results from a volitional act, in other words, an act a person did, committed by another person to cause fear, harm or death. Intent to cause death is a common element but is not required for classification as a homicide, more below.

It is to be emphasized that the classification of homicide for the purposes of death certification is a neutral term and neither indicates nor implies criminal intent, which remains the determination within the province of a legal process.

NELSON: Why is that second part important?

FOWLER: Because this is a medical opinion that is on a death certificate. Manners of death are unique, virtually unique to the United States of America. These were put on the death certificate by the Center for Disease Control in order to gather information as to how Americans died or die for epidemiological purposes and to study and try and prevent deaths.

They are not meant to usurp any kind of legal process. And, in fact, in many circumstances, regardless of what the medical examiner puts on a death certificate in the way of a manner, the legal system can and will act in a completely independent and different format.

NELSON: Now, again, we discussed a little bit about the CDC death certificates, the instructions. Is this the guideline by the CDC?


NELSON: To enter all diseases or conditions contributing to the death that were not reported in the chain of events?

FOWLER: In the first part, yes.

NELSON: Now, back to -- take this down for a moment, Your Honor. So with respect to Dr. Baker's autopsy, I want to talk a little bit about the cardiopulmonary arrest that he references.

What are the findings that were relevant to your analysis in this particular case?


FOWLER: There are substantial pertinent negatives in this particular case that drove my opinion.

NELSON: What about the size of the heart?

FOWLER: So there is, again, certain pertinent positive issues. Mr. Floyd's heart was enlarged. There are multiple methods and studies that have been done on the size of the heart in the United States.

There's one study out of the medical examiner's office in San Antonio, Dr. Molina, and the Mayo, where they took a series of individuals who died suddenly with trauma and hopefully eliminated as part of their process natural disease that might have caused alterations in the heart size.

NELSON: Excuse me, Doctor. Did you prepare a slide relevant to this and if we can publish it?

FOWLER: Yes, I do.

NELSON: So the Molina study you were referencing?

FOWLER: Right. In their study, they found 95 percent of males had a heart weight of between 233 and 383 grams. Anybody outside of those limit, and you would expect about 2.5 percent to be lower and 2.5 percent to be higher. That's the 95 percent certainty on either side of the mean. So that is what they proposed as being the reference range for adult males.

NELSON: How about the Mayo study?

FOWLER: So, the Mayo study is one where you can go in and calculate the weight based on the size of the individual which is potentially more accurate, because you don't want to take a 130-pound 5'5" male and say, you know, and plug him into a particular range. You'd expect their heart to be smaller, as most of their organs would be smaller. Mr. Floyd was a very tall, robust looking individual. I would expect

him to have a larger heart. And so, the type of study, such as the Mayo study, where they put in the sex of the individual, male, the height and the weight, and then come out with -- as part of that calculation accounting for that, the 95th inclusion rate would top out at 510 grams in this circumstance. So Mr. Floyd's heart rate at 540 is outside this range.

I will tell you, there's another -- there are multiple studies. There's another one out of Chicago and Northwestern University which has even broader range and would indicate that Mr. Floyd was within the 95 center, but still right up at the very top end of normal.

The bottom line is he has an enlarged heart.

NELSON: OK. If we could unpublish this, Your Honor.

So in terms of, that's what you ultimately see as relevant evidence, that Mr. Floyd has an enlarged heart?


NELSON: How does the size of the heart affect the blood supply, nutrients, oxygen, things of that nature?

FOWLER; The heart is a muscle and it's dependent on the supply of oxygen, glucose and other important nutrients to function. When a heart or any other muscle grows in size, its consumption of those vital components increases. So, Mr. Floyd's heart would have twice the need of those nutrients compared to a 260-gram heart, 270-gram heart, halfway.

Right in the middle of the Molina study criteria because there's twice as much heart muscle to support, and each of those cells is bigger and requires more oxygen.

NELSON: So it's kind of like the law of supply and demand, right?

FOWLER: Correct.

NELSON: What happens to a person when they experience a lack of supply, so to speak?

FOWLER: So like every other organ, the heart has certain reserves of energy built in. The typical amount of reserve in our brains is enough for us to maintain consciousness for about 10 to 15 seconds. That's the organ which is most sensitive to constant supply.

NELSON: The heart or the brain?


FOWLER: No, the brain. The heart is the next.

But like other organs, it will be able to maintain function even when the supply is reduced or even completely cut off. But at some point, you do have to resupply because those reserves are, when the heart is being exerted or being used, and you either have to completely replace them, or if you only partially replace them, at some point, you're going to exhaust the reserves.

NELSON: So, how do we replenish the supply, so to speak?

FOWLER: The replenishment comes from the coronary arteries. They bring blood into the heart. As that blood arrives, it delivers oxygen and other nutrients, and it also removes the byproducts of the metabolism of those heart muscles as they contract.

NELSON: So what type of symptoms might someone show if they are diminished in their supply?

FOWLER: So at some point, there are a variety of symptoms that can result. You can become -- you can feel your heart racing. You may even get palpitations. You get potentially short of breath.

And in some circumstances, you may start getting chest pain, what we refer to as angina, and it can get even worse than that. You can have sudden symptoms such as a collapse without any warning. There's a spectrum of different symptoms that can occur.

NELSON: So, when the supply isn't being met, what would a person customarily do to replenish the supply?

FOWLER: Well, when one becomes short of breath, you tend to relax, ease up, back off, stop walking, stop running, stop exercising, until such time as you feel like you've got your heart rate down. Some people monitor their heart when they're exercising to make sure they don't go over certain limits. There are different ways.

But, typically, if you experience symptoms, it's your body telling you, slow down.

NELSON: OK. What happens if someone doesn't do that?

FOWLER: If you don't and you don't heed those warnings or you can't heed those warnings because of other circumstances, the consumption of those essential metabolism goes on. The production of the products of contraction which need to be removed continues to increase. And at some point, the heart will fail, have a sudden cardiac arrest/arrhythmia. That's what you expect to see.

NELSON: So, within the field of forensic pathology, what would you call the stopping of the heart?

FOWLER: We typically call it sudden cardiac arrest or cardiac arrhythmia.

NELSON: What's the difference between sudden cardiac arrest and arrhythmia?

FOWLER: Sudden cardiac arrest really is an observational situation. You observe the person suddenly stop functioning, and usually the background process is an arrhythmia of some sort, often starting out as a relatively benign arrhythmia and then progressing into a more malignant arrhythmia which decreases the function of the heart and eventually the heart fails.

NELSON: What types of things might cause a heart to be bigger like Mr. Floyd's?

FOWLER: The commonest one in the United States which is part of the developing world is hypertension, what we would call essential hypertension. It just happens.

NELSON: Based on what you reviewed, did you determine whether Mr. Floyd had hypertension?

FOWLER: The size of the heart would be extremely good evidence that he had hypertension.

Secondly, there are medical records that I did see where he had an elevated blood pressure in previous hospital administrations or previous clinical interactions. So, yes, there's evidence that he had that. And then there was something else found at autopsy, a tumor, that is sometimes associated with hypertension as well in certain people.

NELSON: That's the paraganglioma?

FOWLER: Paraganglioma, yes.

NELSON: Lioma, sorry. We'll talk about that a little bit later.

So, just kind of generally, can you describe the major blood vessels of the heart?

FOWLER: Yes. There are two major, the right coronary artery and the left coronary artery. The left coronary artery, within a very short distance of coming off the aorta, divides into two major arteries, the left anterior descending and the left circumflex.


So, some people call it three coronary arteries, but technically, there are two with one dividing into two. Really, neither description would be incorrect.

NELSON: And what is narrowing or stenosis of the arteries?

FOWLER: The narrowing or stenosis means the arteries, the lumen, the inside diameter of that artery is smaller than it should be. It has been narrowed by a disease process.

NELSON: How does long-term drug use affect narrowing of the arteries?

FOWLER: There are certain drugs that do cause advanced or more rapidly advancing atherosclerosis. Not just drugs, but many substances and toxins. Even smoking, for instance, is associated with earlier atherosclerosis, and certain drugs and other substances can be added on to that. Even urban pollution has a risk of advancing heart disease.

NELSON: What specific drugs?

FOWLER: Well, in this particular case, methamphetamine, which was present in Mr. Floyd, has been associated with earlier onset of narrowing of the coronary arteries by atherosclerosis.

NELSON: And can you describe the difference between proximal and distal narrowing of the arteries?

FOWLER: Right. So, the narrowing can occur anywhere up and down the artery. When it occurs close to its origin, close to the aorta where the blood supply comes from, we will call that proximal. If it occurs far down the artery towards the end of the artery or further down the artery, it's called distal.

The implications are somewhat different. If you have narrowing close to the beginning of the artery, anything downstream from that narrowing is subject to decreased supply of blood.

If you have it further down and distal, then the first part, and all the branches that come off the first part are supplying the heart, and that part of the heart will still receive enough supply. It's not restricted.

But once you get to beyond the narrowing, any tissue, heart tissue, muscle, downstream from that is going to be subjected to a reduced supply.


FOWLER: So in this particular case he had significant narrowing of all of his coronary arteries close to the origin, which really is consistent with all of his heart, unfortunately, being subjected to reduced supply, not just a portion of his heart, but the entire heart.

NELSON: Is there a certain amount of narrowing that forensic pathologists consider to be enough to cause sudden death?

FOWLER: So the typical conventional number that forensic pathologists use is between 70 and 75 percent narrowing is a risk factor for sudden cardiac death.

NELSON: Can you survive with greater than 75 percent narrowing?

FOWLER: Oh, absolutely. I have seen many, many cases where it can be 90, 95 percent. Again, it depends where on the artery it is.

So a proximal narrowing is more dangerous than a distal narrowing, because any part -- full (ph) part of the heart. And in this particular case, we know Mr. Floyd had 90 percent narrowing. So he was walking around with 90 percent stenosis, beyond the 75. That was not affecting him as part of his daily activities.

So when he was at rest, walking around, doing his normal daily activities, I know of no information that he was symptomatic or having any problems. So, yes, you can go beyond 75 percent.

NELSON: That's what cardiologists conclude, you can survive with greater than 75 percent?

FOWLER: Yes. I think the difference is medical examiners see people who have died be 75 percent. Cardiologists see people walking around with 95 percent. So, they see the live population. We see the dead population.

So, we probably end up with different standards based on, unfortunately, that's what we see.

NELSON: So in terms of an autopsy finding, can you describe what myocyte necrosis is and how -- whether that's necessary to diagnose a sudden cardiac death?