Scapegoating refers to blaming a single person or group of people for a negative outcome. The concept itself appears in the Bible, in which a goat or another animal was sacrificed for the sins of others.
Scapegoating may also occur to organizations and corporations. A simple example of scapegoating is blaming the media for real-world violence.
have both of them be right next to each other at the same time and ask them what's going on so they can't lie while being right next to each other. If they both don't fess up just make sure they're always seperated.