It would depend. I could see both the accuser and witnesses being afraid to come forward for fear that they would have to serve time, and the innocent person maybe never being cleared.
I do think that anyone who deliberately makes a false accusation against someone (not a misidentification done in good faith, but knowingly false), once that person is cleared, should be charged with both defamation AND obstruction of justice, with penalties ranging from fines to some time in jail.
Not at all
Yes. Defamation of character is sometimes irreparable...
Yep that would be true justice
Yes...but then they would never admit they lied and the innocent person wouldn't be freed so it probably wouldn't work out so well.