I was taking test shots, to see what kind of results I would get with different settings and with the flash. I wish I could post an example but I'm without a scanner for the next week or two. One of the shots I took was of my son standing on the back of the sofa. All the walls are white. The wall behind my son was 9 feet away from his position. It was a clear day with a lot of light coming through the double doors going out to the balcony. I had thought that with the flash I could reduce the shadows on the side of him that was away from the windows - which it did, but there's also a huge unnatural looking shadow behind him which could only be created by the flash. The shadow certainly wasn't there when I took the photo.

I've seen "flash shadows" in other photos, typically on forums with people still learning (like myself).

My first assumption is that I shouldn't have used a flash at all and that if I need additional lighting I should use another method.

I hope that clarifies what I'm asking.