1. I can't speak Greek well, *whereas* my father can.
2. I can't speak Greek well, *while* my father can.
Both 1 and 2 are correct and have the same meaning right?
3. The murderer was let off *on the grounds that* no evidence had been found.
4. The murderer was let off *due to the fact that* no evidence had been found.
5. The murderer was let off, *for* no evidence had been found.
Are these sentences ok? Do they mean the same ? I guess yes they do. I need confirmation, though.