A medical expert in Derek Chauvin's murder trial defended the cause of death of the victim George Floyd. Dr. Martin Tobin argued that the lack of oxygen claimed the life of the victim of police brutality. It can be remembered that Floyd died after Chauvin pressed his knees on the neck of the victim against a pavement.

Tobin's emphatic defense for Floyd happened on Chauvin's murder trial on Thursday, according to a Fox News report. Tobin rejected the claims of the defendant that Floyd died due to drugs and his underlying health condition.

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George Floyd's Cause of Death, According to Tobin

Tobin, who testified for Floyd, is a physician specializing in pulmonology and critical care, according to a report from TMZ.

Tobin told the jury that Floyd's breathing was severely constricted while the suspect and two other officers are pinning him down on his stomach. The incident happened in May 2020 while the victim was handcuffed behind him.

"A healthy person subjected to what Mr. Floyd was subjected to would have died," said Tobin during the trial. Tobin also works as a lung and critical care specialist in Edward Hines Jr. VA Hospital and Loyola University's medical school situated in Illinois.

Tobin has presented a graphic representation of what happened during Floyd's death. The prosecutors noted that the event lasted for about nine and a half minutes, and for more than 90 percent of the time, Chauvin's knee was "virtually on the neck" of Floyd.

"The cause of low-level oxygen was shallow breathing, small breaths," said Tobin. Tobin furthered that the shallow breaths have no capability to bring air to his lungs down to the essential areas of the organ.

Chauvin's Defense Attorney Eric Nelson pressed Tobin with the misconception of Minneapolis Officers being trained that if people can speak, they can breathe. Tobin disagreed, saying that Floyd talking and moving, as shown in the video, does not mean that the victim is breathing effectively. Tobin also pointed out that the leg movement of Floyd was involuntary.

Chauvin's Defense and Other Testimonies

Nelson told the jury in the previous week that Floyd had taken drugs when the encounter happened. Nelson also argued that the autopsy result showed meth and fentanyl in Floyd's system.

However, it was disagreed with by Forensic Toxicologist Dr. Daniel Isenschmid. Isenschmid noted that the amount of methamphetamine in Floyd's system would be consistent with a prescription dose, and it is "very low." Isenschmid also pointed out that the fentanyl was metabolized, and if it is connected to a fentanyl death, the results will not show that the drug was metabolized.

Dr. Bill Smock also testified on the trial, confirming that George Floyd died from a "positional asphyxia." Smock described the method as a sophisticated way of saying how Floyd died with no oxygen in the body. Smock is a police surgeon for the Louisville metro police department and the head of Training Institute on Strangulation Prevention's Medical Committee.

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WATCH: George Floyd died from low oxygen levels, doctor confirms during Derek Chauvin trial - from Global News