How is Snowball used as a scapegoat?

Snowball is easy for Napoleon to use as his scapegoat because Snowball is not there- he was "expelled" from the farm. Any time something goes wrong on the farm, the windmill falling apart, things disappearing, etc. it's easy to blame Snowball because he is not there to defend himself and the animals don't know any better so they believe it. It's also easy to use Snowball as a scapegoat in the sense that when his ideas are stolen by Napoleon, no one can say for certain that they were Snowball's ideas first. Napoleon even goes as far as to call Snowball a criminal and he relies on the ignorance of the animals and their inability to remember correctly to get them all to believe these things.