fall guy:
(in British English – ‘scapegoat’ — for the right pronunciation of ‘fall guy’, please click here)

the ‘fall guy’
a person who has been cheated by a trick;
an innocent person who is blamed or punished for someone else’s errors, wrong doing, crime, etc. (from the Jewish and Christian scriptures in which the high priest of a community places all the sins of the community on a goats head and lets it to escape into the wilderness so that the whole community is cleansed of its sins); a scapegoat;
a dupe;
an innocent but weak or timid person who is blamed or punished in public in order to save an important or powerful person who is actually responsible for that wrong doing or crime,

Leon Panetta, political fall guy, CIA Director, USA
We were thirteen members who worked on that project and when it failed, I was made the fall guy because I was the team leader.
Though winning a match is a team work and every one of the players and non-players of the team is responsible, there is always a fall guy, like the captain, the coach or the manager, who is blamed for the team’s failure!
In politics, you see some budding politicians who are made fall guys when something goes wrong in the party and the party loses credibility.
You find a number of fall guys in mega multi-million dollar enterprises where the blame is passed on from the top level to the bottom level and settles on those who have no voice or support from others.
