The Case of the Smiley Face

It was when I entered Kathryn's room that I saw it.  A cute little smiley face, drawn in an inappropriate place. 

The bed

The face

There are two suspects, neither of whom have an alibi.  Jocelyn was found at the scene, though she was sitting all the way across the room, peacefully reading a book.  Was she trying to throw me off the scent? Or was it Kathryn, who was in the room earlier, all alone?  Which twin wielded the pen?  Alas, we may never know.....