Maltese camera angle

I have been watching John Huston's "The Maltese Falcon" on the new special restored edition DVD that Warner Bros. putout this year. First off it's a superb set which includes the two previous versions of the film along with many other extras. The quality of the print and transfer is worth it alone.
There is this one scene among many other gorgeous shots that I found particularly interesting. I have done a sketch of it above. Though over-the-shoulder sots are often used in film noir I found the use of the foreground character's (Boghart) body cutting across the frame to enclose the background character (Mary Aster) intriguing.
To setup the shot, Boghart was first sitting back against the couch then leaned forward putting his elbows on his knees in a very natural action.
I love finding places where through natural action or gestures you can find anew camera angle or acting on a character.