Oswald in the doorway: the blog of the Oswald Innocence Campaign, by Ralph Cinque

No, Backes. He doesn't have his thumb on his chest. He has his thumb on his other arm. 

This is approximately what he is doing:

Why would he hold just one arm across his chest? What would be the point? What would it accomplish? Molina's thumb isn't on his chest; it's on his other arm.