Dr. Martin Tobin told the jury that the cause of George Floyd's death was low oxygen levels caused by shallow breaths due to Floyd's body position and the pressure of Derek Chauvin's knee on his neck. STREAM LIVE: Murder trial of Derek Chauvin in the death of George Floyd resumes: https://abcn.ws/39SYlqT Subscribe to GMA's YouTube page: https://bit.ly/2Zq0dU5 Visit GMA's homepage: https://www.goodmorningamerica.com #DerekChauvinTrial #GeorgeFloyd #GMA