The defense in the murder trial of former Minneapolis police officer Derek Chauvin will start presenting its case today. Chauvin is accused of murdering George Floyd last year after holding his knee on his neck for more than nine minutes, an incident that sparked protest across the country and around the world. Judge Peter Cahill said that all evidence should be presented by the end of the week.   Yesterday, the jury heard emotional testimony from Floyd’s brother, while a police use-of-force expert said no reasonable officer would have done what Chauvin did.