@Animandel - I don't go into my attic often, so when I went up there one day, turned on the light and saw a snake skin in the middle of the floor I couldn't believe it. At first I tried to convince myself that the skin was something else. Then I tried to figure out ways it could have gotten there without the snake actually being in my attic.
Once I finally accepted the fact that there was, or at least had been, a snake in my house, I decided I should figure out what type of snake it was. I can't identify the average snake when I see the entire body, I had no chance of identifying it by the flimsy piece of skin in my attic.
I showed the skin to different people and most of them thought it was probably a black snake of some kind. If I had wanted to definitely identify the skin and the snake, I could have taken it to an expert. Each kind of snake has specific patterns on the skin and experts can identify the snake by those patterns. So yes, experts can identify snakes by their discarded skins.