How can I tell whether a person is facing a Kinect or showing it his/her back?
I am using the Microsoft Kinect SDK v1.7.
The Microsoft Kinect SDK does not track the back of users. It is unable to track a full body rotation, but only a more or less forward facing user.
Now granted, it might get "confused" and be able to track your skeleton when you're facing it with your back, but even then the skeleton will be aligned as if you were facing forward. If it does track you could potentially apply a heuristic that says "are my wrists further from the sensor than my hips?" or "how is the shoulder, elbow, wrist angle oriented", but it would all be inaccurate at best.