California became one of the first states to change how police use of force is investigated and prosecuted. Gov. Jerry Brown signed a bill this week that bans the use of grand juries in cases where police use of lethal force is being investigated. Up to now, individual district attorneys had discretion over whether to bring a case before a judge or a grand jury. The new law, which comes after a year of intense national dialogue about police accountability, takes effect January 2016.