The 1980 killing of 16-year-old South Lake Tahoe gas station attendant Richard Swanson is headed to trial.On Tuesday, following a preliminary hearing that lasted several weeks, El Dorado County Superior Court Judge James Wagoner found there is enough evidence against Andrew Sanford for prosecutors to continue their pursuit of a murder conviction against him.Sanford is scheduled to be arraigned March 8 at the main courthouse in Placerville. He has pleaded not guilty to the killing.During Tuesday arguments, prosecutor Patricia Kelliher said DNA found on duct tape used to bind Swanson's hands during the alleged robbery of the South "Y" Shell …