Dr. Martin Tobin and Dr. Bill Smock testified in the murder trial of former Minneapolis police officer Derek Chauvin, charged in George Floyd's death. RELATED: https://bit.ly/3g1dRVD A medical expert in the physiology of breathing testified in the murder trial of Derek Chauvin that the way George Floyd was restrained — handcuffed behind his back, face-down on the ground, with a knee on his neck — prevented him from breathing properly. » Subscribe to USA TODAY: http://bit.ly/1xa3XAh » Watch more on this and other topics from USA TODAY: https://bit.ly/3cTdp9P » USA TODAY delivers current local and national news, sports, entertainment, finance, technology, and more through award-winning journalism, photos, videos and VR.