from The Killer Inside Me
Caitlin Turner first lying on her stomach on a bed in a pair of panties that's pulled up to reveal most of her butt. We then see her bare butt clearly as she kneels on the bed and smacks it with her left hand. Lastly, she is seen lying on the bed again wearing just a bra as she reaches back with her left hand again to spank herself. From The Killer Inside Me.