FACTBOX-Key moments from ninth day of witness testimony at Chauvin trial

DANIEL ISENSCHMID, TOXICOLOGIST WHO TESTED FLOYD BLOOD SAMPLES Isenschmid said the amount of methamphetamine in samples of blood taken after Floyd's death, 19 nanograms per milliliter, was similar to levels a doctor would expect to see in a patient after taking a single dose of the drug in a prescribed form for attention-deficit disorder. He said the concentration of fentanyl in Floyd's blood was 11 ng/ml, and there was evidence a lot of the opioid had been broken down in Floyd's body to norfentanyl, which a doctor would not expect to see in someone killed rapidly in an overdose.

Three medical experts took the stand on Thursday in the murder trial of former police officer Derek Chauvin, where they told the jury that George Floyd was killed by police pinning him to the ground, not a drug overdose. Chauvin, who is white, pressed his knee into the neck of Floyd, a 46-year-old Black man in handcuffs, for about nine minutes on May 25, 2020, a scene that ignited global protests against police brutality.

The county medical examiner has ruled Floyd's death a homicide at the hands of the police, while Chauvin's lawyers have argued Floyd's death was from a drug overdose. Here are some of the important moments from the ninth day of testimony on Thursday:

DR. DANIEL ISENSCHMID, TOXICOLOGIST WHO TESTED FLOYD BLOOD SAMPLES Isenschmid said the amount of methamphetamine in samples of blood taken after Floyd's death, 19 nanograms per milliliter, was similar to levels a doctor would expect to see in a patient after taking a single dose of the drug in a prescribed form for attention-deficit disorder.

He said the concentration of fentanyl in Floyd's blood was 11 ng/ml, and there was evidence a lot of the opioid had been broken down in Floyd's body to norfentanyl, which a doctor would not expect to see in someone killed rapidly in an overdose. Isenschmid also compiled data from his office on samples taken from people stopped for driving under the influence in 2020, noting people addicted to opioids need to take higher doses as tolerance builds up. The average level of fentanyl found in the blood of those people was 9.69 ng/ml, he said.

DR. MARTIN TOBIN, EXPERT IN THE RESPIRATORY SYSTEM Tobin said Floyd's breathing became fatally shallow under the police restraint but that the number of breaths he took per minute did not decrease up until the moment he lost consciousness, contradicting a defense theory.

Tobin said that a fentanyl overdose, in contrast, is marked by a sharp decrease in the frequency of breaths. The shallow breaths resulted from a combination of measures applied by police, including placing Floyd prone on the street, handcuffing his hands behind his back and the officer kneeling on his back and neck, he said.

Tobin unbuttoned his shirt collar at one point and most jurors followed his request to do the same as he felt his neck, describing how Chauvin's knee compressed the delicate tissue of the hypopharynx, blocking that part of the respiratory system in the lower part of the throat. Tobin said videos showed Floyd trying to push his chest up from the street as he struggled for breath beneath Chauvin and two other officers.

"They're pushing the handcuffs into his back and pushing them high, then on the other side you have the street," Tobin said. "It's like the left side is in a vise." Tobin said Floyd's leg could be seen jumping up in an involuntary seizure as his brain was starved of oxygen.

Soon after, Tobin said, the moment came when Floyd did not have even "an ounce of oxygen left in his entire body," although Chauvin's knee stayed on Floyd's neck for three more minutes. In cross-examination, Eric Nelson, Chauvin's lead lawyer, asked Tobin if he had personally weighed Chauvin, who in police reports is recorded as 140 pounds (64 kg), or Chauvin's equipment in order to calculate the pressure applied by the officer's knee. Tobin said he had not.

DR. WILLIAM SMOCK, EMERGENCY AND FORENSIC MEDICINE EXPERT BASED IN LOUISVILLE, KENTUCKY Smock was the last witness to take the stand on Thursday.

"He died because he had no oxygen left in his body," Smock testified, saying Floyd suffered from air hunger. "He is saying: 'Please, please. Get off of me, I want to breathe, I can't breathe.' That is not the fentanyl overdose, that is somebody begging to breathe," he said.

On cross-examination, Nelson centered his questioning on Floyd's methamphetamine and fentanyl use, his heart disease and having had the COVID-19 virus and his physical exertion during the struggle with police officers. There was no evidence that Floyd had a heart attack or a drug overdose, Smock testified.

(Compiled by Brendan O'Brien in Chicago; Editing by Peter Cooney)

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