The elder's manual says there is no such thing as "automatic disfellowshipping". For the most part that is true.
Pretty much, if it is your first offense, and you confessed voluntarily, and you display a lot emotion, and lay it on thick about your "damaged relationship with jehovah", you won't get DF'ed.
But if a case is especially notorious, lots of publicity, you don't have a chance.
The case of the Bethel worker who was caught in a sting operation, trolling young boys for sex, comes to mind. As I recall, 3 elders went down to his jail cell and after a quite perfunctory judical committee told him he was DF'ed. There are threads about that case on here - it was 4 or 5 years ago.