Louise Rolfe was "the blond alibi." She was Machine Gun Jack McGurn's mistress, and she and McGurn holed up in a Chicago hotel during the St. Valentine's Day Massacre in order to establish that McGurn wasn't present at the shooting.
Q. Who was the only man that Capone killed with his own hands after he left Brooklyn? (Hint: it wasn't Scalisi, Anselmi or Giunta, who were still breathing after he baseball-batted them and were dispatched by his bodyguards.)