Falling from any height could be fatal especially if you hit your head or broke your neck when falling.
Peoples have died when they fell from as high as 6 to 15 feet in the air.
So while you're less likely to die from a fall of 6 to 15 feet high you can still die and that fall can be fatal.
However a definite fatal fall would probably 50 to 100 feet high or even higher.
The higher you go the better the chance that it will be fatal.
If you fall from 1,000 feet or more without a parachute then it's certainly gonna be fatal unless the person is really lucky.