Derek Chauvin is on trial for George Floyd's death

Dr. Martin Tobin, a pulmonologist, said during rebuttal testimony that the opinion of defense expert witness Dr. David Fowler regarding George Floyd's potential level of carbon monoxide in his blood was "simply wrong."

Tobin said medical records showed Floyd's oxygen saturation was 98% when he died. Prosecutor Jerry Blackwell asked him: "Does that tell us anything whatsoever about what the carbon monoxide content could have been at a maximum?" 

Tobin said: "Yes, it does. It tells us that if hemoglobin is saturated at 98%, it has – for others is 2%. So the maximum amount of carbon monoxide would be 2%." 

Why this is important: Dr. Fowler testified that it was possible that carbon monoxide ingestion could have been one of the causes of Floyd's death. He based this on observations of Floyd being pinned on the ground near the tailpipe of the police cruiser that officers were trying to get him into. Fowler acknowledged that he had not seen any data on Floyd's carbon monoxide levels prior to testifying.

During his testimony Fowler said that it was his opinion that Floyd's carbon monoxide levels in his blood could have increased by 10% to 15%. Tobin said that assessment is "simply wrong."

Watch:

As the prosecution recalled Dr. Martin Tobin as a rebuttal witness at the Chauvin trial, CNN legal analyst Laura Coates says the pulmonologist will have to be on the "on the shortest, tightest leash possible" to ensure the judge does not declare a mistrial.

Tobin previously testified that it was his opinion that George Floyd died from low oxygen levels, and he will now be rebutting the testimony of defense expert witness Dr. David Fowler, a retired forensic pathologist.

"The judge has been very clear he will declare a mistrial because any hint, any suggestion or mention of the Hennepin County data will be prejudicial to a defendant who gave notice through their witness expert about a theory of carbon monoxide poisoning. And they did not have the data disclosed to them in time to be able to potentially fully flush it out or to recoil on their own theory," Coates explained.

She added:

"Appellate courts have no tolerance for prosecutors who do not disclose information in a timely fashion and try to get it through a rebuttal witness. And so, this prosecution team is going to have to be extraordinarily prudent. And I hope that this witness, as informative as he is, can stay ton that leash."

The risk is that witnesses can be like wild cards, just like jurors, Coates explained.

"I don't care if you are the most seasoned expert testifying witness. Sometimes they do not understand the implications of their slip-ups or making a statement ... Defense attorneys are always on guard with this very point," she said. "In the event of a conviction, they want to have their ducks in a row of how they can seek an appeal to overturn based on, especially, prosecutorial misconduct or any allegations based on that."

The prosecution has called Dr. Martin Tobin, a pulmonologist, as a rebuttal witness at the Chauvin trial.

Tobin is rebutting the testimony of defense expert witness Dr. David Fowler, a retired forensic pathologist.

Tobin previously testified that it was his opinion that George Floyd died from low oxygen levels.

Defense attorney Eric Nelson just rested the defense's case in the Derek Chauvin murder trial.

Prior to that, Chauvin declared in court that he would invoke his Fifth Amendment privilege and not testify.

What happens next: The prosecution is expected to call one rebuttal witness today.

After the defense rests its case, Judge Peter Cahill will allow the prosecution to call a witness to rebut some of the testimony by defense expert witness, Dr. David Fowler. But the judge said that he will limit what the witness can testify about.

During a court proceeding this morning prior to the jury coming in, both sides argued over the rebuttal testimony.

Prosecutor Jerry Blackwell told the judge that the prosecution had new evidence to present regarding carbon monoxide in George Floyd's blood. Yesterday, Dr. Fowler, a retired forensic pathologist, said it was possible that carbon monoxide ingestion from the tailpipe of the car that Floyd was pinned on the ground near could have contributed to his death.

Defense attorney Eric Nelson said he opposed allowing the prosecution to present this evidence and call its rebuttal witness. Nelson argued that the disclosure of these new test results was untimely. He said that he only received the information last night after court had wrapped for the day.

The prosecution indicated in court that the witness they will call to rebut Fowler's testimony is Dr. Martin Tobin, a pulmonologist that testified at trial that Floyd died of "low oxygen levels."

The judge ruled that Tobin can testify however, he is not allowed to tell the jury about the test results. He said that any mention of these records will result in a mistrial.

Moments ago, Derek Chauvin told the court he would not testify in his own defense in the George Floyd murder trial. 

Chauvin invoked his Fifth Amendment right when he chose not to testify.

According to the White House, the Fifth Amendment "provides that citizens not be subject to criminal prosecution and punishment without due process."

Here's the full amendment:

Ex-Minneapolis Police officer Derek Chauvin just said he will invoke the Fifth Amendment and not testify at his murder trial.

The defense also does not have the burden of proof, she added.

"He never had the burden to prove his innocence. It always remained with the prosecution. And now, the jury will be instructed, per his request, that they are not to draw any inference from his decision not to testify," Coates explained.

Defense attorney Eric Nelson just explained to his client that he has the right to testify at the trial. Derek Chauvin just said that he will invoke the Fifth Amendment and not testify.

Here was their exchange:

Nelson: Have you made a decision today, whether you will attempt to testify, or whether you intend to invoke your Fifth Amendment right? 

Chauvin: I will invoke my 5th amendment privilege today. 

The judge then asked Chauvin if the decision was his. He said it was.

See the moment:

The 14th day of testimony is set to begin soon in the murder trial of former Minneapolis police officer Derek Chauvin.

Chauvin is charged with second-degree unintentional murder, third-degree murder and second-degree manslaughter in the death of George Floyd, who died in May 2020 after Chauvin placed his knee on Floyd's neck while he pleaded, "I can't breathe."

Yesterday, Maryland's former chief medical examiner testified for Chauvin's defense that Floyd died due to his underlying heart disease — not the police restraint.

That testimony cuts at the prosecution's argument, bolstered by five separate medical experts, that the primary cause of death was Chauvin's restraint of a handcuffed Floyd in the prone position — known as "positional asphyxia." To get a guilty verdict, prosecutors have to prove that Chauvin's actions were a "substantial causal factor" in Floyd's death.