Derek Chauvin is on trial for George Floyd's death

By Melissa Macaya, Mike Hayes, Melissa Mahtani, Veronica Rocha and Fernando Alfonso III, CNN

Updated 2334 GMT (0734 HKT) April 8, 2021
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6:42 p.m. ET, April 8, 2021

Here's what happened today in the Derek Chauvin trial

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Three medical experts testified today about why they believe George Floyd died and what was found in his system in May 2020.

Here's what they said today during the trial of former officer Derek Chauvin:

Dr. Martin Tobin, a physician in pulmonary and critical care medicine, testified after having reviewed the medical records in the Floyd case.

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

PEA means pulseless electrical activity, "which is a particular form of abnormal beat of heart — an arrhythmia," he explained.

He also shared his opinion on the cause for the low level of oxygen in Floyd. "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."

Tobin also testified that fentanyl did not have an effect in "causing depression of the respiratory centers" in Floyd. Tobin said that with fentanyl, Floyd's respiratory rate should have been 10, instead the rate was at 22, which is normal.

"Basically it tells you that there isn't fentanyl on board that is affecting his respiratory centers. It's not having an effect on his respiratory centers," Tobin told the prosecution.

Tobin noted that the normal range for a respiratory rate is between 12 and 22. Tobin testified that Floyd's respiratory rate was 22 just before he lost consciousness.

Dr. William "Bill" Smock, emergency medicine physician with specialized training in forensic medicine, testified that Floyd died because of a lack of oxygen in his body.

"Mr. Floyd died from positional asphyxia. It is a fancy way of saying he died because he had no oxygen left in his body," Smock said. "When the body is deprived of oxygen, in this case from his chest pressure and back, he gradually succumbed to lower and lower levels of oxygen until it was gone and he died."

Smock also discussed the nature of strangulation and whether bruising is something that always occurs. "You can be fatally strangled, die of asphyxia, and have no bruising. The presence or absence of a bruise on a human body, is dependent upon a multiple different variables. How much pressure is applied? How is that pressure applied? How frequently is that pressure applied?" Smock said.

Dr. Daniel Isenschmid testified that fentanyl and methamphetamine were found in the blood taken from Floyd at the hospital. Floyd’s fentanyl concentration was 11 nanograms per milliliter, Isenschmid said. Norfentanyl, a drug that it breaks down into, was recorded at a level of 5.6, he said.     

The norfentanyl concentration could indicate fentanyl was taken and then some of it had already broken down, or it could indicate someone took a dose of the drug, then later took another dose, Isenschmid explained.  

The impact of fentanyl on someone can vary person to person, due to tolerance, he said.

6:42 p.m. ET, April 8, 2021

Court has adjourned for the day

Court is adjourned until tomorrow morning when testimony is expected to resume in the trial of former Minneapolis Police officer Derek Chauvin.

Dr. William "Bill" Smock, an emergency medicine physician with specialized training in forensic medicine, wrapped up his testimony this afternoon.

He told the court that there was no evidence that George Floyd had a heart attack.

Smock said Floyd died because of a lack of oxygen in his body.

"When the body is deprived of oxygen, in this case from his chest pressure and back, he gradually succumbed to lower and lower levels of oxygen until it was gone and he died," Smock said.

5:57 p.m. ET, April 8, 2021

Floyd should have received CPR once officers could not find a pulse, emergency medicine physician says

Dr. William "Bill" Smock, an emergency medicine physician with specialized training in forensic medicine, testified that officers should have begun administering CPR (cardiopulmonary resuscitation) to George Floyd the moment they couldn't feel a pulse.

Smock's comments were made following a question from prosecuting attorney Jerry Blackwell during the trial of former police officer Derek Chauvin.

Blackwell: "At what point should CPR have been commenced with respect to Mr. Floyd?"
Smock: "Way before it was; as soon as Mr. Floyd is unconscious he should have been rolled over. We have documentation on the video that the officer says 'I cannot find a pulse.' ... "But clearly, when they couldn't find a pulse, CPR should have been started."

5:40 p.m. ET, April 8, 2021

Someone can be fatally strangled and have "no bruising," emergency doctor says

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Dr. William "Bill" Smock, an emergency medicine physician with specialized training in forensic medicine, testified about the nature of strangulation today and whether bruising is something that always occurs.

"You can be fatally strangled, die of asphyxia, and have no bruising. The presence or absence of a bruise on a human body, is dependent upon a multiple different variables. How much pressure is applied? How is that pressure applied? How frequently is that pressure applied?" Smock said during the trial of former officer Derek Chauvin who has been charged in the death of George Floyd.

Smock added: "You can be strangled to death and still have no bruises."

6:42 p.m. ET, April 8, 2021

Emergency medicine doctor says Floyd died because "he had no oxygen left in his body"

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Dr. William (Bill) Smock, emergency medicine physician with specialized training in forensic medicine, testified today that George Floyd died in May 2020 because of a lack of oxygen in his body.

"Mr. Floyd died from positional asphyxia. It is a fancy way of saying he died because he had no oxygen left in his body," Smock said during the trial of former officer Derek Chauvin. "When the body is deprived of oxygen, in this case from his chest pressure and back, he gradually succumbed to lower and lower levels of oxygen until it was gone and he died."

5:33 p.m. ET, April 8, 2021

Forensic toxicologist says Floyd's blood contained fentanyl and methamphetamine

From CNN’s Aaron Cooper

Fentanyl and methamphetamine were found in the blood taken from George Floyd at the hospital, a forensic toxicologist testified in the trial of former Minneapolis Police officer Derek Chauvin.   

Floyd’s fentanyl concentration was 11 nanograms per milliliter, Dr. Daniel Isenschmid, from private testing company NMS labs told the jury. Norfentanyl, a drug that it breaks down into, was recorded at a level of 5.6, he said.     

The norfentanyl concentration could indicate fentanyl was taken and then some of it had already broken down, or it could indicate someone took a dose of the drug, then later took another dose, Isenschmid explained.  

The impact of fentanyl on someone can vary person to person, due to tolerance, he said.

Looking at a collection of fentanyl tests conducted in DUI cases for comparison, Isenschmid said the level found in Floyd’s blood was in the top quarter, the 80th percentile.  

The amount of methamphetamine in the blood was low, he testified. It was consistent with what someone would receive in a single, legally prescribed, dose.  

Morphine was found in Floyd’s urine, but not in his blood, Isenschmid testified, which could indicate the drug had been taken earlier since it remains in urine longer than blood.   

The opioid addiction treatment suboxone was found in Floyd’s blood, as well as generic Narcan, THC, nicotine and caffeine.

On cross examination Isenschmid discussed reporting limits and traces of drugs that were found but were not reported because they were so low. 

Defense lawyer Eric Nelson noted if a representative of the state crime lab testified and refused to acknowledge the possibility of the presence of a drug, that could, theoretically, be because of those threshold rules.

Since fentanyl on the street is not manufactured in a controlled environment, it can vary from dose to dose, Isenschmid testified.   

He agreed that the comparisons he cited for the prosecution did not include certain information, including if other drugs were present and what happened to the person.

On re-direct examination Isenschmid compared the ratio of fentanyl to norfentanyl in Floyd’s blood tests, and says it was more similar to a collection of patients that were alive instead of dead.

5:02 p.m. ET, April 8, 2021

Forensic toxicologist explains why the ratio for methamphetamine to amphetamine in Floyd wasn't reported

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Dr. Daniel Isenschmid, a forensic toxicology from NMS Laboratory in Horsham, Pennsylvania, testified today about why the lab he works at didn't report the ratio of methamphetamine to amphetamine in George Floyd following the May 2020 incident.

"We didn't look at the ratio for methamphetamine to amphetamine with Mr. Floyd because it was below the reporting limit; is not on the report and we didn't report it," Isenschmid said in response to a question from defense attorney Eric Nelson during the trial of former officer Derek Chavin.

In a cross examination by prosecutors, Isenschmid said that Floyd's methamphetamine were indeed lower than 94% of the driving under the influence population.

Some context: Three forensic scientists on Wednesday testified that several white pills containing fentanyl and methamphetamine were found in Floyd's vehicle, and a smaller pill with Floyd's saliva on it was found in the back of the police squad car.

Today, Dr. Martin Tobin, a renowned pulmonary critical care doctor, testified that fentanyl did not play a role in Floyd's death.

After observing body-camera footage, Tobin calculated Floyd's respiratory rate at 22 breaths per minute, within normal range. People who overdose on fentanyl generally have a respiratory rate of about 10, so Tobin concluded that fentanyl was not affecting Floyd's breathing.

"Basically it tells you that there isn't fentanyl on board that is affecting his respiratory centers. It's not having an effect on his respiratory centers," Tobin said.

4:21 p.m. ET, April 8, 2021

Why fentanyl keeps coming up during the trial

Forensic expert witnesses have testified about fentanyl, which has come up several times during the trial of former police officer Derek Chauvin.

Three forensic scientists on Wednesday testified that several white pills containing fentanyl and methamphetamine were found in George Floyd's vehicle, and a smaller pill with Floyd's saliva on it was found in the back of the police squad car.

Today, Dr. Martin Tobin, a renowned pulmonary critical care doctor, testified that fentanyl did not play a role in Floyd's death.

After observing body-camera footage, Tobin calculated Floyd's respiratory rate at 22 breaths per minute, within normal range. People who overdose on fentanyl generally have a respiratory rate of about 10, so Tobin concluded that fentanyl was not affecting Floyd's breathing.

"Basically it tells you that there isn't fentanyl on board that is affecting his respiratory centers. It's not having an effect on his respiratory centers," Tobin said.

The pulmonologist also said that any pre-existing health conditions Floyd suffered from prior to the incident in May 2020 did not cause his death.

Why this matters: During the trial, defense attorney Eric Nelson has focused on Floyd's use of fentanyl and methamphetamine and his resistance to the arresting officers.

3:57 p.m. ET, April 8, 2021

A forensic toxicologist is now testifying at the trial

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The next witness to testify at the trial is Dr. Daniel Isenschmid. He is a forensic toxicology from NMS Laboratory in Horsham, Pennsylvania.