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Prosecution Questions Forensic Toxicologist in Chauvin Trial. Aired 3:30-4p ET

Aired April 8, 2021 - 15:30   ET



DR. DANIEL ISENSCHMID, FORENSIC TOXICOLOGIST: And then if you pass the examination the board votes on your final certification.

After that, you have to do continuing education each year and obtain a minimum number of continuing education credits and then every five years you have to reapply to the board for re-accreditation.

ERIN ELDRIDGE, PROSECUTING ATTORNEY: And have you gone through all those requirements and satisfied them successfully?

ISENSCHMID: Yes, I have.

ELDREDGE: And are you up to date with all of those continuing education requirements as well?


ELDREDGE: I want to get back to your role as sort of as a forensic toxicologist. Could you describe sort of your day-to-day job duties as a forensic toxicologists at NMS Labs?

ISENSCHMID: So my primary responsibility at NMS Labs is to do case review, and what that means is when toxicology tests are performed at NMS Labs, particularly ones that require many kinds of tests to be done, they wind up being reviewed by a toxicologist or certifying scientist to look at them, in the context that all the testing that was done.

So individual tests are reviewed by analysts in a laboratory, and they are secondary reviewed as well, but the final review comes to either a toxicologist or certifying scientist that looks at everything in the context of the entire case.

ELDREDGE: And then in that capacity is it part of your job duties to author reports and sign off on all that testing?

ISENSCHMID: Yes, it is.

ELDREDGE: Approximately how many cases have you reviewed in that capacity as a forensic toxicologist? ISENSCHMID: I review about 7 to 8,000 case per year.

ELDREDGE: And in terms of the work that comes into NMS Labs, are there a variety of agencies that submit samples to NMS Labs for testing?

ISENSCHMID: Yes, we get samples from medical examiners and coroners. We get samples from police agencies for DUI cases and we also get a lot of clinical samples from hospitals and referral laboratories.

ELDREDGE: So in that capacity does NMS receive both postmortem, or death related samples as well as samples from living patients?

ISENSCHMID: Yes, we do.

ELDREDGE: And NMS as a lab, approximately how many tests or samples does NMS receive for testing each day?

ISENSCHMID: We receive about 12 to 1,300 requisitions each day.

ELDREDGE: And when you say requisition what is that?

ISENSCHMID: It would mean requests for testing. It could be multiple samples on the requisition.

ELDREDGE: So thousands of test a year.

ISENSCHMID: Thousands of tests a day.

ELDREDGE: Tens of thousands of tests a year. My math is bad.

All right, is NMS a licensed and accredited lab?


ELDREDGE: And does that include national accreditations as well?

ISENSCHMID: National and state accreditations.

ELDREDGE: I'm going to turn to your work in this particular case. Did NMS Labs receive some samples for testing from the Hennepin County Medical Examiner's office related to George Floyd?


ELDREDGE: And were there a number of different samples that were received?


ELDREDGE: What were the samples that were ultimately tested by NMS Labs?

ISENSCHMID: So that we tested the samples that were requested by the Hennepin County Medical Examiner to be tested. So we tested samples that were labeled as hospital blood and we also tested urine that was collected at the autopsy. ELDREDGE: And in terms of the testing that was performed at NMS Labs

did -- were those tests pursuant to standard operating procedures at the lab?

ISENSCHMID: Yes, they were.

ELDREDGE: And that process was followed for all of those tests?


ELDREDGE: Getting the results from that testing, what were the notable findings from that testing?

ISENSCHMID: Some of the most notable findings in the hospital blood was the presence of fentanyl, at 11 nanograms per milliliter.

And then the metabolite of fentanyl, the breakdown product of fentanyl, norfentanyl had a concentration of 5.6 nanograms per milliliter.

In addition we found methamphetamine at 19 nanograms per milliliter.

ELDREDGE: So I'm going to talk about each of those substances one by one. And you indicated these were the results from the hospital blood in this case, is that right?

ISENSCHMID: That is correct.

ELDREDGE: So let's start with methamphetamine. What is methamphetamine?

ISENSCHMID: So methamphetamine is a central nervous system stimulant. It can actually be prescribed. It rarely is, but it can be prescribed under the brand name digoxin. And it is used for attention deficit hyperactivity disorder and obesity. It was also an experimental use for treatment of narcolepsy.


And between 2016, 2018 there were about 10,000 prescriptions in the U.S. written for digoxin that year -- each year.

ELDREDGE: So can methamphetamine be both, a street level recreational drug and also a prescription drug?


ELDREDGE: With respect to the results, the 19 nanograms per milliliter that you found of methamphetamine, what significance, if any, is there to that amount?

ISENSCHMID: Well, that is actually approximately the amount that you would find in the blood of somebody given a single dose of methamphetamine as a prescribed drug.

ELDREDGE: So when you say you described the prescription drug form in which methamphetamine can be available, the results would be consistent with the prescription dose of that, is that right?

ISENSCHMID: Yes, it could be.

ELDREDGE: Would that be considered a low level of methamphetamine?

ISENSCHMID: Yes, very low.

ELDREDGE: And you also talked about the fentanyl results of 11 nanograms per milliliter? First, what is fentanyl?

ISENSCHMID: So fentanyl is an opioid analgesic. It's used similar to morphine, and it's much more potent than morphine. It can be used to treat pain and also be an adjunct used in surgery for anesthesia.

ELDREDGE: And you talked about opioids. Maybe you can just describe what an opioid is?

ISENSCHMID: So it's a -- opioids are actually include both natural semi-synthetic and synthetic drugs that act on the mu receptor which are where opioids act.

Opiates are a natural product that are found in the poppy plant such as morphine and codeine. So opiates are opioids but not all opioids are opiates.

ELDREDGE: So what are some examples of opioids?

ISENSCHMID: So fentanyl would be an example of an opioid.

ELDREDGE: Would oxycodone also be an opioid?

ISENSCHMID: Yes, it would.

ELDREDGE: And then you talked about similarities between opioids and opiates. Is that right?


ELDREDGE: And you mentioned morphine as an opiate.


ELDREDGE: Is that heroin?

ISENSCHMID: So heroin is actually made from morphine, but when heroin breaks down, it breaks down into a metabolite called 6-acetylmorphine. And then eventually to morphine

ELDREDGE: So heroin would break down into 6-acetylmorphine and morphine? Is that right?


ELDREDGE: Do opioids and opiates have similar effects?

ISENSCHMID: Yes. ELDREDGE: Getting back to the fentanyl level in this case, you

mentioned it was 11 nanograms per milliliter, can fentanyl levels vary widely depending on an individual?

ISENSCHMID: Yes, the can.

ELDREDGE: And why would that be?

ISENSCHMID: Because of tolerance.

ELDREDGE: And could you just explain how an individual's drug tolerance might affect the impact a particular drug like and opioid or fentanyl might have on them?

ISENSCHMID: So if a person becomes tolerant to a drug you need to have more and more of the drug to get the desired effect, so with chronic use to get the same feeling that you would at a given concentration of fentanyl you need to take more to get that effect.

ELDREDGE: And so if somebody is regularly using opiates or opioids would that individual then develop a tolerance to a drug like fentanyl?


ELDREDGE: All right, now you also talked about norfentanyl, could you just describe what norfentanyl is?

ISENSCHMID: So when the body gradually eliminates fentanyl, it breaks it down from fentanyl to norfentanyl, that's a gradual process that occurs over time and it's one of the ways the body eliminates fentanyl.

ELDREDGE: And you indicated that the amount of norfentanyl found in the hospital blood in this case was 5.6 nanograms per milliliter, is that right?


ELDREDGE: And what is significant about that amount of norfentanyl?

ISENSCHMID: Well, it shows that some of the fentanyl was metabolized to norfentanyl. It also could mean there was pre-existing norfentanyl with additional fentanyl given on top of that.

But basically shows that when we see very recent deaths with fentanyl we frequently see fentanyl with no norfentanyl whatsoever because after a very acute fentanyl intoxication the body doesn't have time to break it down.

ELDREDGE: And you described when you see a fentanyl overdose, typically you may not see norfentanyl or low levels of norfentanyl?


ELDREDGE: In addition to those findings from the hospital blood were there some other findings as well that were included in your report?

ISENSCHMID: There were. There were some incidental findings, and I believe there was codeine, which was from smoking and there was caffeine, and there was evidence of prior marijuana use, by the presence of cannabinoids.


I would have to look at the report to know.

ELDREDGE: And would that refresh your recollection?


ELDREDGE: If we could put on the screen just for the witness's recollection, Exhibit 624, please.

And then if we could zoom in on the positive findings portion. All right, referring to your report now, could you describe the other findings with respect to this case?

ISENSCHMID: Yes, so the additional finding was a compound called 4-APP and that is actually a precursor to fentanyl manufacturing, but it is

also a metabolite of fentanyl, it's not pharmacologically significant and that's probably mostly inactive. But it was measured as part of some additional testing that was requested by the Hennepin County Medical Examiner.

And then the urine findings we had presumption of positive findings not confirmed for cannabinoids, amphetamines, and fentanyl, those were not confirmed because they are present in the blood. So that follows that.

And then we also had findings for opiates in the urine and we were asked to confirm those. And we found a concentration of morphine in the urine of 86 nanograms per milliliter.

ELDREDGE: Apologies. Sorry, you were saying you found morphine in the urine, 86 nan grams per milliliter, is that right?


ELDREDGE: And was that morphine found in the blood?

ISENSCHMID: No, it was not.

ELDREDGE: And can a finding of morphine in the urine be indicative of prior use in advance of time of death?

ISENSCHMID: Yes, it can, you can see morphine in urine for several days depending on the dose and prior use pattern.

ELDREDGE: And again, is that because it shows up in urine longer than blood?

ISENSCHMID: Yes. ELDREDGE: So you have tested both hospital blood as well as the urine,

you described the findings in the urine with respect to morphine, you are also discussing the 4-APP finding in the hospital blood.

With respect to the other findings in your report. Can you just sort of summarize what they were and whether they were significant at all?

ISENSCHMID: So I think I mentioned sort of was caffeine, which is present in many of us. And cotinine which is present as a metabolite of nicotine from smoking.

And then cannabinoids, there was Delta 9 THC at 2.9 nanograms per milliliter. And it's breakdown product, 11 hydroxy Delta 9 THC at 1.2 nanograms per milliliter.

And then the inactive Delta 9 carboxy THC at 42 nanograms per milliliter.

ELDREDGE: And when it comes to these THC findings -- or relating THC relating to cannabinoids, what if any impact does that have?

ISENSCHMID: It's very hard to interpret those given the nature of the samples and also what happens with cannabinoids because they go into the fat so they can be released slowly with time, and certainly, you know, anything like CPR or something like that is potentially going to release THC from the fat, so it doesn't really mean a whole lot of living cannabinoids we use at some point in time.

ELDREDGE: So they can remain in the system and be detected for an extended period of time. Is that right?


ELDREDGE: OK. We can take that down. Thank you.

Now as part of your testing process at NMS Labs, were there also some metabolites or other substances that were detected as part of testing but below your lab's reporting limits?

ISENSCHMID: So we did find other substances that were below the threshold to report, and that is why they are not on the report, but they are in part of the data package that was requested, and, you know, one can see those there.

ELDREDGE: And do keep those litigation packages of that data as part of your standard operating procedures over the course of business at NMS Labs?

ISENSCHMID: So all of that data is part of the course of the business, the litigation package is actually pulled from that data on request, but yes.

ELDREDGE: So as part of your testing, the lab's testing of the samples in this case, I'd like to ask about the testing process for methamphetamine and whether there were findings of amphetamine? ISENSCHMID: Sure. So when we had a positive -- the screen was positive

for methamphetamine by a method called LC time-of-flight mass spectrometry.

And anything that's positive above a certain threshold by that procedure is then confirmed by an alternate procedure. In this case methamphetamine was positive on the screen, and we ran a confirmation test for amphetamines.


Amphetamines confirmation test actually consists of ten compounds, but we are only interested in the target compounds that we are actually confirming in this case. So in this case we did detect methamphetamine, and because it's a metabolite of methamphetamine there was evidence of amphetamine, but it was below the reporting limit, so it was not reported.

ELDREDGE: And you indicated that amphetamine is a metabolite of methamphetamine, is that right?


ELDREDGE: And does that mean then that the body breaks down methamphetamine into amphetamine over time?

ISENSCHMID: Yes, it does.

ELDREDGE: In addition to confirming the presence of amphetamine was there also an indication on initial testing of buprenorphine?

ISENSCHMID: There was an indication on the LC time-of-flight screen. But because it was below the reporting limit, it was not confirmed so it's merely an indication.

ELDREDGE: And when you say indication that just means it didn't go through that second step of the process, is that right?


ELDREDGE: What is buprenorphine?

ISENSCHMID: Buprenorphine is a drug that's prescribed. It's called suboxone and it's typically prescribed for opioid agonist therapy for people that are going through opiate treatment.

ELDREDGE: And are the components of suboxone, both buprenorphine but also naloxone?


ELDREDGE: And is naloxone essentially generic Narcan?


ELDREDGE: Getting back to the blood that was tested in this case, you indicated that it was hospital blood, is that right?

ISENSCHMID: That's correct.

ELDREDGE: What's significant about using hospital blood for testing?

ISENSCHMID: Well, hospital blood is -- if it's anti-mortem blood is more representative of what is actually circulating in the body prior to the time of death. After death, there are changes that occur with drug concentrations particularly in central blood got collected from the heart.

That's a phenomenon known as postmortem redistribution where drugs go from areas of higher concentration to lesser concentration.

That is less of an issue with peripheral blood samples such as femoral blood, but it can still occur. So it's ideally you would want to try to get a sample as close to the time of death as possible.

ELDREDGE: And if a blood sample is taken after death or after extensive CPR on a patient can there be some postmortem redistribution?

ISENSCHMID: I think that's possible. There's a lot you don't know but it certainly is possible and if it does, it tends to increase concentrations.

ELDREDGE: And when you say increase concentrations, does that mean that the level might show higher than it actually was at the time of death?


ELDREDGE: What about hemolysis? What's hemolysis?

ISENSCHMID: Hemolysis is the breakdown of a red blood cell.

ELDREDGE: And does that -- or did it have any impact on the testing in this case?

ISENSCHMID: No, I mean, that would have an impact on certain clinical chemistry tests like potassium which is stored in red blood cells but when you analyze a blood sample for drugs you are analyzing a whole sample so it would have no effect.

ELDREDGE: So you mentioned that NMS Labs receives thousands of samples a day, tens of thousands of samples a year, did you review and compile some data from the year 2020 with respect to NMS's fentanyl cases and methamphetamine cases?


ELDREDGE: And would those help you to contextualize the results in this case?


ELDREDGE: Your Honor, I would offer for demonstrative purposes, Exhibit 920.

JUDGE PETER CAHILL, HENNEPIN COUNTY: Any objection for the use for demonstrative purposes?

And what was the number again, Ms. Eldridge?

ELDREDGE: Sorry, your Honor?

CAHILL: Exhibit number?


CAHILL: 920 is received for demonstrative purposes only, which means members of the jury, it won't go back with you for deliberation, but it will be received for (INAUDIBLE) witnesses testimony.

ELDREDGE: And if we could publish. Thank you, your Honor.

All right, Dr. Isenschmid, I'm going to have you describe what's shown on the screen.

ISENSCHMID: So as of right now, we're looking at what happens when fentanyl is metabolized over time into norfentanyl, so gradually the amount of fentanyl starts to decrease and the norfentanyl starts to increase.


ELDREDGE: And that's what happens as the body metabolizes fentanyl? Is that right?

ISENSCHMID: That is correct.

ELDREDGE: Next slide please. And could you describe what's shown here, please?

ISENSCHMID: So this is data from NMS Labs from year 2000. And we looked at the fentanyl concentrations in postmortem cases, specifically in those and only those that were collected in peripheral blood. Again for the reasons I mentioned before. Central blood like cardiac blood can have a significant postmortem distribution. So we wanted to look at samples that had a minimal amount of that.

ELDREDGE: I think you indicated the year 2000, is this data from 2020?

ISENSCHMID: Sorry, 2020, my mistake. So this from the year 2020. And we have 19,185 cases that we looked at. And in the peripheral blood in these postmortem cases the mean fentanyl concentration, average fentanyl concentration was 16.8 nanograms per milliliter, and the median concentration was 10, median being 50 percent above and 50 percent below.

ELDREDGE: And with respect to you, peripheral blood, you indicated that chose the samples that would have minimal postmortem redistribution. Is that right? ISENSCHMID: Correct.

ELDREDGE: And why is that in comparison to this case?

ISENSCHMID: Because the sample that we had of hospital blood is probably going to have less issues with postmortem redistribution than we would have had, had it been postmortem blood.

ELDREDGE: And then these cases that represented as postmortem cases, are these cases that you would be getting from ME's offices or coroners' offices?


ELDREDGE: And where the individual would be deceased or dead?

ISENSCHMID: Correct. We also looked at the norfentanyl concentrations and those were 6.01 as a mean, and the median down at 2.2 nanograms per milliliter.

ELDREDGE: So just to clarify with respect to these postmortem cases the average level of fentanyl was 16.8 nanograms per milliliter, and the average level of norfentanyl was 6.01 nanograms per milliliter, is that right?


ELDREDGE: Next slide please. What's shown here?

ISENSCHMID: So this slide shows postmortem cases with no norfentanyl. Again for the year 2020.

So out of those 19,185 cases we had 15,455 that included fentanyl and norfentanyl but there were 3,724 cases with no norfentanyl.

There are 6 that were exceptions that for reasons of testing purposes. But those ones that were only fentanyl but no norfentanyl.

ELDREDGE: So does this slide indicate that there was a significant number, this 3,724 cases where there was fentanyl found but no norfentanyl at all?


ELDREDGE: All right. Next slide, please. What's shown here?

ISENSCHMID: So this is, switching gears, this is we're looking at DUI driving under the influence fentanyl concentrations that we found in 2020. So these are blood samples that are sent to NMS Labs for people that were suspected of driving under the influence of drugs or potential other reasons, the way they were driving.

And in this case, we tested -- we had 2,345 cases that were individuals that were alive that had fentanyl on board. Of course, other drugs may also be present. But this was specifically looking at fentanyl. And we had a mean concentration of 9.5 nanograms per milliliter, median of 5.3. and then for norfentanyl, a mean of 5.42 and median of 2.2.

ELDREDGE: And again, just to clarify, for these 2,345 cases, those individuals were alive. Is that right?


ELDREDGE: And you indicated the average fentanyl level. I believe, is 9.59 nanograms per milliliter, is that right?


ELDREDGE: And the average norfentanyl level for those cases was 5.42 nanograms per milliliter. Is that right?


ELDREDGE: Next slide, please? And what's shown here?

ISENSCHMID: So this is just a breakdown of the fentanyl concentrations we found in drivers that were alive. So almost the majority of them were under 5 nanograms per milliliter of fentanyl.

And then we had another 26.3 percent that were between 5.1 and 10 nanograms per milliliter.

And then the next set of data was we had 216 cases which were between 11 and 15 nanograms per milliliter. So that would be in the same area of Mr. Floyd's level of 11 nanograms per milliliter.

And then we had several -- quite a few cases that were even greater than that.


We had a 109 between 16 and 20, 81 that were between 21 and 26. 133 between 26 and 50. And then we actually have 53 cases in living subjects where the fentanyl was greater than 15 nanograms per milliliter.

ELDREDGE: So comparing Mr. Floyd's level to the driving population where individuals were alive, his level was within a quarter of the pie of the DUI cases that NMS Labs has received, is that right?

ISENSCHMID: Right, he would be right in there with about the 80th percent percentile.

ELDREDGE: And you indicated that those levels for drivers were found in 53 cases higher than 50 nanograms per milliliter, is that right?


ELDREDGE: So those individuals were alive and essentially driving at that time?

ISENSCHMID: Yes, and pretty amazing.

ELDREDGE: All right. Next slide, please. And what's shown here?

ISENSCHMID: So this is basically a postmortem concentration or samples of -- hospital blood samples that were submitted for Mr. Floyd -- for Mr. Floyd and we found fentanyl at 11 nanograms per milliliter and norfentanyl at 5.6 nanograms per milliliter.

ELDREDGE: Next slide, please. So this slide shows what the ratio of the parent drug to the metabolite is, so 11 nanograms per milliliter divided by 5.6 the norfentanyl, gave Mr. Floyd a ratio of fentanyl to norfentanyl of 1.96.

ELDREDGE: And essentially, does this slide show just the way in which you would calculate the fentanyl to norfentanyl ratio?


ELDREDGE: Next slide, please. So what's shown on this slide?

ISENSCHMID: So this slide shows the ratios of fentanyl levels between 9 and 13 nanograms per milliliter. So that range was chosen because Mr. Floyd's concentration was 11 nanograms milliliter.

And when we do driving-under-the-influence work we actually assign an uncertainty of measurement to that result. So if a driver had an 11 nanogram per milliliter fentanyl present, we would report that as 11 nanogram per milliliter plus or minus 2 nanograms per milliliter.

So I did this to see, well, what kind of rations do we see between postmortem and DUI cases when the fentanyl level is between 9 and 13 nanograms per milliliter, what kind of ration do we see?

And we can see in the postmortem cases, the mean ratio of fentanyl and norfentanyl was 9.05 with a median of 5.88 versus the DUI population where the mean was 3.2, median 2.24.

ELDREDGE: And then just to clarify, in the bar that shows the postmortem cases where there are 3,088 cases that you looked at between the range of 9 to 13 nanograms per milliliter?

ISENSCHMID: Yes, between 9 to 13 nanograms per milliliter.

ELDREDGE: And the ration in the postmortem cases was 9.05 on average, is that right?


ELDREDGE: And then with respect to the DUI cases you were looking at 275 cases between the range of 9 and 13 nanograms per milliliter, is that right?

ISENSCHMID: That's correct.

ELDREDGE: And so the average ratio within that group was 3.20, is that correct?

ISENSCHMID: Yes. ELDREDGE: How does Mr. Floyd's ratio compare to that data set?

ISENSCHMID: So Mr. Floyd's ratio is roughly just a little bit below the median ration in DUI. So in postmortem cases we know fentanyl concentrations can be much higher than norfentanyl concentrations because frequently these are deaths due to fentanyl.

Other drugs may be present and there could be other reasons for the death. It doesn't say these are all fentanyl intoxications. But just looking at it as a whole, large amount of data, this is what we observed.

And we know with the DUI population, they are alive but other drugs may be present as well. So it's really just to sort of look at how things look differently in the living and postmortem population.

ELDREDGE: And does this slide also show that Mr. Floyd's ratio was below the average and even below the median for that found in DUI cases?


ELDREDGE: OK. Next slide please.

BROOKE BALDWIN, CNN HOST: So you see what the prosecution is trying to prove with this toxicologist there up on the stand, essentially that it was not the level of drugs in George Floyd's system that killed him that day, May 25th of last year.

But in fact, they're arguing it was former police officer Derek Chauvin's knee on his neck and his back. The trial continues on.

I'm Brooke Baldwin. Thank you so very much for being with me. We'll see you back here tomorrow. THE LEAD with Jake Tapper starts right now.

JAKE TAPPER, CNN HOST: Welcome to THE LEAD. I'm Jake Tapper.