Yes. There is a ritual called Soulguard. You cast it on a willing target or yourself who then spends a healing surge. If this character dies before the end of the day, he instead regains hit points of his surge value. No you just need a delayed variant of this ritual. (lets say, after three rounds) Not unreasonable that a powerful guy tries to get this ritual or at least some scrolls of this to be prepared for a difficult fight.
The alternative: If the BBEG is just a henchman of another BBEG use another ritual. I call it "Dispose Minion". When the BBEG is interrogated, he can use a keyphrase (or the BBEG in the background, who watches the interrogation via another ritual) to instantly kill the prisoner. This way, the prisoner can give some hints, but before the important things he just dies in some spectacular way.