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Live Coverage of Derek Chauvin Trial; Pulmonologist Martin Tobin is Questioned by the Prosecution; Composite Animation And Video Stills Presented in Trial. Aired 10:30-11a ET

Aired April 8, 2021 - 10:30   ET



MARTIN TOBIN, PULMONOGIST: It's also the premier journal in the world for intensive care medicine, and it's the official journal of the American Thoracic Society.

JERRY BLACKWELL, PROSECUTING ATTORNEY: Have you taught and lectured outside of Illinois and-or Texas?


BLACKWELL: Generally where?

TOBIN: I've lectured all around the world. I mean, I've lectured in more than 30 different countries around the world, and probably the vast majority of states within the United States.

BLACKWELL: Minnesota is one of the states in the United States. How about Minnesota?

TOBIN: I have lectured in Minnesota. I've been in the Mayo Clinic several times as a lecturer.

BLACKWELL: Were you given an award from the Mayo Clinic?

TOBIN: Yes, I was given an award called the (INAUDIBLE) lecturer in the Mayo Clinic. And they give it out to one doctor every 10 years, and it's only to one doctor. It doesn't matter what specialty, so it could be around neurosurgery, gynecology, whatever, they just pick one person every 10 years.

BLACKWELL: And was it for anything in particular that you were recognized by the Mayo Clinic?

TOBIN: No, just for my work in -- as a researcher in clinical medicine.

BLACKWELL: Have you also published in basic science journals such as the "Journal of Applied Physiology"?

TOBIN: Yes, I've published a lot of work on basic science that wouldn't necessarily be directly related to medicine in the "Journal of Applied Physiology."

BLACKWELL: The jurors may not be familiar with what physiology is as a science. Could you generally explain it?

TOBIN: Yes. Physiology is basically how the body works. You want to know the science of how it works, you want a deeper understanding of what are really the mechanisms that make the body does what it does.

BLACKWELL: Within the field of physiology, is there a particular focus or interest you have?

TOBIN: I'm primarily interested in breathing, in the (INAUDIBLE) area. And so with breathing, that would mean how the brain regulates your breathing, how the brain sends signals down to the muscles that can throw your breathing, your diaphragm, your ribcage.

And then how you expand your chest and how you overcome forces within your chest, like resistance within your chest and all the rest of it, to get air moving in and out of your lungs. And then the particular forces that you generate in terms of the pressures within your chest that will enable breathing to occur with the ultimate purpose of getting oxygen in and getting rid of carbon dioxide.

BLACKWELL: And you consider this a part of the study of medicine?

TOBIN: It's not quite as part of the study of medicine, it's really quite separate because it's more the basic physiology. So it's more in the realm of math and physics. But then it's applied over because to be a good doctor, you need to have a good knowledge of science. But the science part is really separate from the medical part. And it's to try and hone (ph) down on the science as best as possible.

BLACKWELL: How long have you been working in respiratory physiology?

TOBIN: Since 1981, forty years.

BLACKWELL: And what exactly drew you to the physiology of breathing?

TOBIN: Because I was going into pulmonary, at that stage, I knew as (ph) already directed, I'd spent five years doing lung disease. And I just wanted to really know how you breathe. And I wanted to come up with new knowledge because everybody thought everybody knew everything of how to breathe, and I thought it would be fun to find a lot of new stuff.

BLACKWELL: So, doctor, do you know of others kind of in your field who have been studying respiratory physiology for 46 years?

TOBIN: No. I mean, I know an awful lot along (ph) the way, but I mean, I would know no more than a handful or less of people who are still doing physiology at the patient's bedside, no. After 46 years.

BLACKWELL: So, doctor, let's change subjects and talk a little bit about your experience of work as -- serving as an expert. Have you served as an expert witness before?

TOBIN: Yes, I have.

BLACKWELL: What types of cases? TOBIN: Practically all of them have been in medical malpractice, so

I've done it for both the plaintiff, for the patient side, and I've done for the defense, for the physician side.

BLACKWELL: Have you ever been involved in a criminal case before?

TOBIN: No, I have never been involved in a criminal case.

BLACKWELL: Have you testified in court before?

TOBIN: I have testified in court. I don't keep track of the numbers, but I suspect I've been in court about 50 times.

BLACKWELL: Would you tell the ladies and gentlemen if you're getting paid for your time in this case?


TOBIN: No, I am not getting paid.

BLACKWELL: And why is that?

TOBIN: Well, when I was asked to do the case, I thought I might have knowledge that would be helpful to explain how Mr. Floyd died. And since I'd never done this type of work in this nature before, I decided I didn't wish to be paid for it.

BLACKWELL: So did you volunteer to the state of Minnesota, or did the state of Minnesota call you?

TOBIN: The state of Minnesota contacted me.

BLACKWELL: What were you asked to do, Dr. Tobin?

TOBIN: I was asked to review the medical records related to the case. These were medical records from Hennepin County, then there were a number of interviews of people that were interviewed. I was given a long list of these. And primarily, it was related to looking at a large number of different videos. Of course then the big part was that I needed to read on the scientific background of all the various aspects related to it.

BLACKWELL: So let's talk about your opinions with respect to this case. Have you formed an opinion to a reasonable degree of medical certainty on the cause of Mr. Floyd's death?

TOBIN: Yes, I have.

BLACKWELL: Would you please tell the jury what that opinion or opinions are?

TOBIN: Yes. Mr. Floyd died from a low level of oxygen. And this caused damage to his brain, that we see, and it also caused a PEA arrhythmia that caused his heart to stop.

BLACKWELL: And by PEA, you mean pulseless electrical activity? TOBIN: Correct, it's a particular form of an abnormal beat of the

heart, an arrhythmia, a particular form of it.

BLACKWELL: Is this what some persons might refer to as asphyxia?

TOBIN: Yes, it has been called asphyxia. To me, it's not terribly helpful, it just -- what we're really talking about is a low level of oxygen. Other people talk about hypoxia, that again is just a Latin term meaning a low level of oxygen. So all of this is just really other words for a phenomenon that is a low level of oxygen.

BLACKWELL: Have you formed an opinion to a reasonable degree of medical certainty as to what the cause is or was for the low level of oxygen in Mr. Floyd?

TOBIN: Yes, I have.

BLACKWELL: Would you tell us what that is?

TOBIN: The cause of the low level of oxygen was shallow breathing, small breaths, small tidal volumes, shallow breaths that weren't able to carry the air through his lungs, down to the essential areas of the lungs that get oxygen into the blood and get rid of the carbon dioxide. That's the alveoli at the bottom of the lung.

BLACKWELL: Dr. Tobin, would using a short video that you prepared help you explain to the jurors how oxygen gets into the lungs in the body? How we take in oxygen?


BLACKWELL: I'm going to show you what's been marked as exhibit 950. Can you describe first what that is?

TOBIN: So here, we're looking at the lungs inside a body and we see here that you can see the windpipe up at the top, the trachea, and then that splits into the bronchial tubes. And also you can see the diaphragm down at the bottom. And when the diaphragm contracts, it will -- there will be a movie (ph).

BLACKWELL: So the jurors can't -- the jurors can's see it yet, so I'm just having you just identify it.

TOBIN: Oh, I'm sorry, terribly sorry, I apologize.

BLACKWELL: Yes, I'm going to offer it (ph), your honor.


BLACKWELL: Exhibit 950.



BLACKWELL: Yes, please proceed. We can -- we'll display it so the jurors can see it.

TOBIN: OK, so now we're looking, and you can see the contraction of the diaphragm -- that's the kind of pink area down at the bottom -- we see air going down through the windpipe, and then proceeding down to the bronchial tubes. And then it was going to continue down the bronchial tubes, onto the (ph) reach (ph) out to the air sacs, which will be the alveoli.

And now we're seeing that we're moving down here, and these are like the grapelike structures down at the bottom. And this is where all the action occurs. The oxygen goes across those air sacs, and also the CO2 goes across them, then it's expelled back out.

So that's everything in a very rapid video.

BLACKWELL: So then what do you -- what happened in the case of Mr. Floyd that relates to the shallow breathing that resulted in his low oxygen?

TOBIN: So there are a number of forces that led to -- that he's -- the size of his breath became so small. And so there are a series of forces higher up that are leading to that, and the main forces that are going to lead to the shallow breath are going to be that he's turned prone on the street, that he has the handcuffs in place, combined with the street, and then that he has a knee on his neck, and then that he has a knee on his back and on (ph) his side.

All of these four forces are ultimately going to result in the low tidal volume, which gives you the shallow breaths that we saw here. And so the air will not be able to reach those air sacs we just saw in the video, where the oxygen is exchanged and the carbon dioxide is removed.

BLACKWELL: Doctor, is there a concept that -- in the respiratory medicine field known as dead space?

TOBIN: Yes, there is.

BLACKWELL: How does that relate to Mr. Floyd?

TOBIN: So if you take (ph) the video back, all the way until you saw those clusters of grapes, where you saw the blood vessels surrounding the alveoli, everything up to there is dead space. So as you're breathing in, you breathe in through your nose, your mouth, it goes down through your windpipe, down through the bronchial tubes, radiating out until it reaches the air sacs.

Up to you get to the air sacs, it's all dead space because the reason we call it is because no oxygen can get across those bronchial tubes, no carbon dioxide can get across it. The oxygen and the carbon dioxide, the only place that gets across is those little grapelike structures. So everything in the lungs before that is dead space.

BLACKWELL: So you mentioned several reasons for Mr. Floyd's low oxygen, and I just want to capture those for the jury and then we'll talk about them. You mentioned one, handcuffs and the street, right?

TOBIN: Correct.

BLACKWELL: You mentioned knee on the neck?


BLACKWELL: Sorry for my writing. You know what I didn't get an A at in school.

The prone position?


BLACKWELL: And then the knee on the back, arm and side. Were those the four?

TOBIN: Yes, these are the four.

BLACKWELL: OK. So we want to talk about each of these. But before we do that, might it be helpful for explaining your testimony to the jury, for them to see the relative positioning of the various officers on Mr. Floyd's body when he was subdued on the ground?

TOBIN: Yes, I think that will be very helpful.

BLACKWELL: Did you assist in preparing an illustration to show the relative position of the officers on the ground?

TOBIN: Yes, I did.

BLACKWELL: And let me show you what's been marked as exhibit 949. Could you just tell us, just describe generally for the record what it is?

TOBIN: I mean, I watched the videos and certain segments of the videos hundreds of times, and it's very difficult to kind of get an overall view of where everybody is positioned, because you're seeing different videos from different angles.

And so the artist has taken all the different videos here, and he's combined them into one moment in time and you can see here. And also, he will remove the police vehicle, so you're going to get a better view. So you're looking kind of at a bird's eye view of where Mr. Floyd is lying and where the officers are positioned in relationship to Mr. Floyd.

BLACKWELL: All right. So the purpose of this is to show the relative positions of the officers on the --


TOBIN: Correct.

BLACKWELL: Your honor, we'd offer exhibit 949. CAHILL: Any objection?

UNIDENTIFIED MALE: No, your honor.

CAHILL: Nine forty-nine is received.

BLACKWELL: So what -- at what point in time, if you say -- told us that this was at a particular point in time?

TOBIN: Right, it's a particular point in time. I don't remember the exact minutes, second at the top of my head but it is like --

BLACKWELL: That's 8:21 and 44 seconds?

TOBIN: That's exactly correct.

BLACKWELL: Is that about right?




POPPY HARLOW, CNN ANCHOR (voice-over): OK, it appears -- OK, there we go.

BLACKWELL: OK, so let's walk through exhibit 949, Brad (ph), if you could advance? And doctor, tell us what we're seeing.

TOBIN: OK, yes.

Now you can see the car is being rotated, you're able to see Officer Chauvin, you're able to see Officer Keung, and then Officer Lane down at his feet. You see underneath Mr. Floyd -- and now the car is being rotated.

Now the car has been removed, and so you're able to see how they're positioned at different points. In terms of -- with Officer Chauvin, with his left knee on the neck, his right knee on Mr. Floyd's arm and chest, and then you can see here, Officer Lane holding his legs, and then you can see Officer Keung with his knee on his torso.

BLACKWELL: So this represents a snapshot in time, as you told us. Did the officers' positions change over time as they were there on the ground?

TOBIN: Yes, they -- the officers' positions changed over time, and also the position of Mr. Floyd himself changed over time. And these become relevant in how we evaluate everything.

BLACKWELL: And was it something you factored into your analysis then?


BLACKWELL: Did you consider where Mr. Chauvin's left knee was during the encounter?

TOBIN: Yes. For Officer Chauvin's left knee, is virtually on the neck for the vast majority of the time.

BLACKWELL: And when you say vast majority, are you able to be more specific?

TOBIN: It was more than 90 percent of the time, in my calculations. There are certain times where it becomes difficult because you don't get a good view of where to -- so for example, I know that Officer Chauvin's right knee is on his back 57 percent of the time. The reason I'm not able to say for the 43 percent is that I don't get a good view. I can -- other times, don't have a good view of exactly where it is.

BLACKWELL: So did you focus on the first five minutes and few seconds?

TOBIN: Yes, I focused on the first five minutes, three seconds because that is up to the time that we see evidence of brain injury.

BLACKWELL: So if Mr. Chauvin's right knee was on his back from time to time, at other times it was placed where in your observation?

TOBIN: It was placed on his arm or -- and then rammed into Mr. Floyd's left chest, so really whether you're making a distinction of whether the knee is on the chest per se or whether it's on the left arm and rammed in against the left chest, from the point of view of breathing, the effects are extremely similar.

BLACKWELL: So let's -- let's turn to the number one on the -- the --


BLACKWELL: Oh yes, then the dot (ph) cam (ph). So I wanted to turn back to the notes, that the number one here, that the -- written down for the reasons you told us for Floyd's low oxygen, Mr. Floyd's low oxygen? Handcuffs and the street, to talk about the first --



BLACKWELL: Could you first, Dr. Tobin, tell us how these various mechanisms, the four that you've discussed, handcuffs and the street, knee on the neck, prone position, kneed on the neck, back, knee on the back, arm and side. How do those mechanisms fall into your work of either respiratory physiology or clinical medicine?

TOBIN: They don't have an awful lot to do with clinical medicine, but they are directly related to my work in physiology, so in understanding the forces that the body has to cope with. These become -- these are crucial (INAUDIBLE) terms (ph) that the various forces that involved in physiology.

BLACKWELL: So then turning to the first one, in handcuffs and the street, the very first one, what is the effect of the handcuffs in the context of what happened to Mr. Floyd?

TOBIN: The handcuffs are extremely important in Mr. Floyd. But the handcuffs on their own, just handcuffs per se, are not that important, it must be the handcuffs combined with the street. And it's because of the positioning of the handcuffs at the back, then how he's manipulated with the handcuffs by both Officer Chauvin and by Officer Kueng, how they manipulate the handcuffs. And they're pushing the handcuffs into his back, and pushing them high.


Then on the other side, you have the street. So the street is playing a crucial part because he's against a hard asphalt street, so the way they're pushing down on his handcuffs, combined with the street? His left side -- and it's particularly the left side we see that, it's like the left side is in a vice. It's totally being pushed in, squeezed in from each side: from the street, at the bottom, and then from the way that the handcuffs are manipulated.

It's not just the handcuffs, it's how the handcuffs are being held, how they're being pushed, where they're being pushed that totally interfere with central features of how we breathe.

BLACKWELL: So Mr. Floyd then is pancaked (ph) between the pavement underneath him and then force on top of him?

TOBIN: Precisely.

BLACKWELL: Now, could you help us to explain how this mechanism, the handcuffs and the street, how does that explain the shallow breathing that you described?

TOBIN: Yes, so this gets back to how we breathe, and this is fairly simple. So the way we breathe, we have two big muscles that help us with breathing. We have the diaphragm, and we have the ribcage muscles. The diaphragm does about 70 percent of what we need for breathing, and about 30 percent of it comes from the ribcage.

And there's -- when the diaphragm contracts or the ribcage contracts, they expand the chest. And when you expand the chest, then air flows in from outside, and it's coming in. And that's all that happens on inspiration.

But to expand the chest, there's two crucial actions that have to happen, and we've referred to these by the terms "pump handle" and "bucket handle." So if -- bucket handle is simple. So if you have a regular bucket that you carry water with and you lift up the handle of the bucket, the handle comes up like this. And so when you contract your diaphragm, you are performing a bucket-handle movement of your -- on the ribcage.

So you contract your diaphragm like that, and each time as you inspire, you can see it yourself. As you inspire -- each of you there in the jury. You inspire, you see that your ribcage is going outwards like that, that's a bucket-handle movement. The second movement that you have is called the pump handle. And this

reflects to an old water pump that would be in the yard for pumping out water. And so you have the handle at the top of the pump, and you lift up the handle of the pump, each time, and the water comes out the spout at the bottom. So you're filling up your container of water.

So with that action, you're lifting up here, this refers to the front- to-back movement of the chest wall. So with the pump handle, your chest goes out with each breath.

And so you can do it yourself. As you take a deep breath, you can feel that front to back, you're expanding your chest, the front-to-back expansion of your chest is with your pump handle. At the same time -- you're doing both of them at the same time. At the same time you're doing that, your chest is expanding from side to side, and that's with your bucket handle. So both of these are occurring.

And these are vital. Without these, you can't breathe. If you don't have the bucket handle working and the pump handle working, there's nothing happening, there's no air going to get in there.

BLACKWELL: Doctor, do you have a photograph that you brought that would help to better understand the pump handle and bucket handle?


BLACKWELL: Let me show you, it's been marked as state's exhibit 951. Do you recognize what this photograph depicts?


BLACKWELL: Is it an accurate portrayal of a certain incident, disaster?

TOBIN: Yes, yes.

BLACKWELL: Would it help to explain the testimony?

TOBIN: Yes. So this is an event that happened in England --


BLACKWELL: Just a second, doctor. Dr. Tobin, just one moment.

TOBIN: -- I apologize, I apologize.

BLACKWELL: Yes, I need to offer (INAUDIBLE), your honor. We offer exhibit 951.

CAHILL: Any objection?


UNIDENTIFIED MALE: Yes, I have an objection to this (INAUDIBLE) sidebar?

CAHILL: All right, sidebar.

JIM SCIUTTO, CNN ANCHOR, NEWSROOM (voice-over): This is a sidebar, a question has been raised about a slide that the doctor was going to use to help explain the breathing process. Judge asked the defense if they had an objection, and they said they did, so they're having what's called a sidebar now to discuss the decision on this.

Laura, these happen in trials. You heard the objection there, why would the defense have an objection to this particular kind of slide?

LAURA COATES, CNN SENIOR LEGAL ANALYST: Well, ultimately because it is effective. I mean, the idea of having the audience, the jurors have an actual understanding, away from the technical aspects of pulmonology and into actually seeing it play out, as if this is precisely what's happening.

Remember, it's a composite, it's not actually in real time like the videos we've already seen. So the composites can be problematic for the defense to say you're reinventing the -- creating a narrative here.


HARLOW: Also the --

SCIUTTO: Let's go back here to --


HARLOW: -- yes, and the judge just sustained that objection, which is notable. Let's listen.

SCIUTTO: That is, let's listen in.

TOBIN: -- the police and the handcuffs, particularly on the left side. So they were forcing his left wrist up into his chest, forcing it in tight against his chest, forcing it high up. And you have to keep in mind that the opposite side of this is the street. So he was being squashed between the two sides.

And so this meant that he couldn't exert his pump handle because, I mean, the street totally blocked his pump handle, there was no way he could do any front-to-back movement. And again, the way they were pressing in on the back, there was absolutely no way that he could do any front-to-back movement.

Then in addition, because of the knee that was rammed in against the left side of his chest -- sometimes the knee was down on the arm or in against the chest, so these would have the same effects.

So basically on the left side of his lung, it was almost like a surgical pneumonectomy. It was almost to the effect as if a surgeon had gone in and removed the lung. Not quite, but along those lines. So there was virtually very little opportunity for him to be able to get any air to move into the left side of his chest. So he was going to be totally dependent on what he would be able to do with the right side. BLACKWELL: Have you selected any footage from the body-worn cameras

that you feel depicts Mr. Floyd's struggles to breathe?


BLACKWELL: I'm going to show you what's been marked as state's exhibit 944.

And first, would you describe what it is?

TOBIN: What you're seeing here is on the --

BLACKWELL: Dr. Tobin, the jurors aren't seeing it yet, it's just describing it for the record.

TOBIN: Oh, I'm sorry.

CAHILL: This is just (INAUDIBLE) on what it is.

TOBIN: They will not see this, I'm describing what I'm seeing?

BLACKWELL: For now, yes.

TOBIN: Yes, OK, that's fine.

What I'm seeing is that his left hand is being grabbed by the police officers, so that's a handcuffed left hand and it's being pushed into his chest. So he's just not able to expand that.

In addition, you'll -- what I'm seeing --


TOBIN: Oh, I apologize, I apologize --

BLACKWELL: What it is.

TOBIN: -- I didn't --

BLACKWELL: So let's hold off and turn it --


TOBIN: I'm sorry, my misunderstanding.

BLACKWELL: Your honor, we'll offer state's exhibit 944.

CAHILL: Any objection?

UNIDENTIFIED MALE: No, your honor.

CAHILL: Nine forty-four is received.

BLACKWELL: All right. Now, Dr. Tobin, the jurors can see it.

TOBIN: OK, I apologize. BLACKWELL: So would you -- no, no, it was quite all right. Would you

tell us what's the significance?

TOBIN: So I mean, now you're able to see here, with the yellow arrow, you're able to see that the officer is holding Mr. Floyd's left hand, he's holding it very firmly, there's a very firm grasp on it. And then Mr. Floyd's left hand is being pushed in against his chest.


Also, we're able to see just on the side, that Officer Chauvin's knee is coming in, and that's compressing in against his side as well.