A 'scapegoat' is someone who is blamed or punished for the mistakes made or wrongs done by others usually because it is more convenient to blame them than the real people at fault or because it is faster. "John, not being able to run away as fast as the others became the scapegoat of the group." "Minister Rourke was an easy scapegoat from much of the parties shady dealings." This is quite a formal expression often used in reporting and the media.