evidence: A police trainer has testified that ex-officer Derek Chauvin was not trained to use his knee in a neck restraint as he did during George Floyd's arrest. [...] Mr Chauvin, 45, was filmed kneeling on Mr Floyd for over nine minutes during Mr Floyd's arrest last May. [...] The footage of Mr Chauvin, who is white, with his knee on African-American Mr Floyd's neck sparked global protests against racism.