WASHINGTON (AP) - Sen. Barbara Boxer on Tuesday called for the death penalty for the killer of a San Francisco police officer and asked the U.S. Attorney's office to prosecute the case. "I hope you will come into this case as a prosecutor to assure the public that the full force of the law will be brought to bear and that the killer pays the ultimate price for his actions," Boxer wrote in a letter to Kevin Ryan, U.S. Attorney for the Northern California. The San Francisco Chronicle reported last week, citing unnamed sources, that the U.S. Attorney's office was...