evidence: Two medical doctors and a forensic toxicologist testified on Thursday in Derek Chauvin's murder trial in the death of George Floyd. Both doctors testified that Floyd died of a lack of oxygen after he was pinned to the ground with his hands cuffed behind him and Chauvin's knee on his neck. The forensic toxicologist said that the fentanyl found in Floyd’s system was lower than levels found in 94% of DUI cases. [...] A renowned pulmonary expert testified that he calculated Derek Chauvin’s knee was on George Floyd’s neck for more than 3 minutes after "there was not an ounce of oxygen left" in his body. [...] MINNEAPOLIS — Officer Derek Chauvin had his knee on George Floyd’s neck — and was bearing down with most of his weight — the entire 9 1/2 minutes the Black man lay facedown with his hands cuffed behind his back, a use-of-force expert testified Wednesday at Chauvin’s murder trial.