By all means, sentence Bob for kidnapping, stick him in jail, have him get out, put a tracker on him and forbid him to leave the country. Then, when Alice pops out and is dead, you just trial him again. It's a different crime! What's more, even if it was the same crime, it'd be material new information!

(Quoth the ECHR: "The provisions of the preceding paragraph shall not prevent the reopening of the case in accordance with the law and penal procedure of the State concerned, if there is evidence of new or newly discovered facts")