If you focus on a focal plane that is sufficiently in front of your subject, or past it (relative to depth of field), the subject will appear blurry. Is there some way of telling purely from the resulting blur if focus was too near or far?
EDIT: the original question has now gotten some good answers, but I noticed it got misinterpreted a couple of times. That indicates it wasn't posed clearly enough, so I edited it a bit. Furthermore I'll illustrate the point a bit more below.
Take this setup with subject, lens and film or sensor in which the subject is sharply focused (the focal plane intersects with it).
Now imagine if the focus is placed behind the subject. This is called "back-focus". The projection of the subject onto the film/sensor becomes blurry, with the actual convergence point for light from the subject being behind it. Light point sources from the subject become discs (or a bokeh shape specific to the aperture).
Next, put the focus in front of the subject. This is called "front-focus". The projection again becomes blurry, but this time because the convergence point for light from the subject is in front of the film/sensor. So the blurred projection is actually inverted.
The question was then, is this difference in blur in some way identifiable through nothing but the resulting picture?
As for the reason for asking, I shoot film so I don't have immediate feedback regarding the result. I keep notes of my shots but I don't have EXIF data, so things such as focal length and distance to subject are an approximation at best. Sometimes I shoot in low light and have to rely on manual focus. Things look sharp in the viewfinder but after development I find out focus has been slightly missed. Being able to figure out if it was too near or too far is then very useful, and can teach me whether it was user error and how to pay attention to it, or whether a specific camera or lens seems to have slight focusing issues and how I might compensate for that.