When Mahone, who is high from drugs, approaches Scofield in his cell, he holds the knife in his right hand with its tip to the wall. At first he holds the knife at the handle. In the next cut it is seen that he holds the knife at the blade with his fist to the wall. A second later he holds it at the handle again with his thumb at end of the knife.
The position of Bellick's hands as he rats out Scofield about the power box.
When Bagwell kills the drug dealer inside his cell and takes the plastic bag off the dealer's head, Bagwell's left hand changes position in between shots going from the dealer's left arm to under his chin.
On Season 3 there's a scene where Sammy and Lechero invite Brad Bellick to watch the soccer match on TV. Sammy refers to the match as the "World Cup", but it was just a game from the Brazilian national league, between Gremio and Fluminense clubs.
When Lechero's cronies take Bellick into Lechero's "cell", one of the guys tell him that the match on the television is one from the world cup. But this is not possible as teams at the world cup wear uni-colored jerseys (a notable exception being Croatia), but never the striped ones as we see the players in the match wearing. The match is clearly one from the Brazilian league.
When the drug dealer is carried out of the prison he is fully clothed. Every other scene when a prisoner dies he is stripped of his clothes by other inmates.
Even after Michael unearths the electrical inspection cover, the other inmates keep on digging for no reason.