Behind the scenes, there's bad news for prosecutors in the upcoming murder trial of ex-BART police Officer Johannes Mehserle.The trouble comes in the form of eyewitness statements to police who investigated the fatal shooting of Oscar Grant and depositions in the lawsuit that led to a $1.5 million settlement from BART for the slain man's daughter.Mehserle has been charged with murder for shooting Grant as the Hayward man lay face down on the Fruitvale Station platform in Oakland while being detained by officers early Jan. 1, 2009. Mehserle's lawyers say he shot Grant by accident while thinking he was firing...