It’s day nine of testimony in the Derek Chauvin trial. The state called its first medical expert witness of the day–Dr. Martin Tobin specializes in pulmonology and breathing. Dr. Tobin testified today that “Mr. Floyd died from a low level of oxygen and this caused damage to his brain that we see and it also caused a PEA arrhythmia that caused his heart to stop.” Dr. Tobin added, “the cause of the low level of oxygen was shallow breathing, small breaths, small, tiny volumes, shallow breaths that weren’t able to carry the air through his lungs.”Based on the video evidence he’s seen, Dr. Tobin cited the handcuffs, Floyd’s prone position in the street, and the officers’ knees on Floyd’s back and neck as factors in Floyd’s inability to breathe. Tobin testified that in its prone position, the left side of Floyd’s body was like it was “in a vice” the way he was being pressed into the street by officers. Key expert testimony today in the Derek Chauvin trial. Several times during his restraint, Floyd said “I can’t breathe.” On cross-examination, defense attorney Eric Nelson asked Dr. Tobin, “if a Minneapolis police Lt. who trains Minneapolis police officers testified that it is frequently said and trained to police officers that a person can talk a person can breathe, you would have a problem with that?” Tobin replied, “Yes, I mean they’re able to breathe at that moment in time, but 10 seconds later they may be dead.” During a key moment in his testimony, while watching video of Chauvin on top of Floyd the moments before his death, Dr. Tobin testified about Floyd “you can see his eyes, he’s conscious and then he isn’t, that’s the moment the life goes out of his body.”