evidence: Derek Chauvin justified in his use of force against George Floyd, witness tells murder trial | CBC News Loaded Derek Chauvin justified in his use of force against George Floyd, witness tells murder trial Former Minneapolis police officer Derek Chauvin was justified in using his knees to pin down George Floyd, a use-of-force expert testified on Tuesday, contradicting testimony by former and current city police officers who said Chauvin's actions violated policy and were excessive.