My answer (I graduated from law school yesterday, so my knowledge of property law is two years old) is to look at it in steps:
OK. At this point Alice is a non-zombie, living human. The conveyance vests in her and she owns in (IIRC) fee simple subject to condition subsequent.
At this point comes the crucial question: Is a zombie legally “alive”? I’m thinking the answer is yes; just as a patient with irreversible brain damage is legally alive, a zombie is still a living person, just horribly diseased.
That’s good thinking on Chris’s part. Decapitation is a sure way to kill zombies. I’m thinking at this point that, when Alice dies, Blackacre would go into trust for Chris on his 21st birthday (if possible), OR it would revert to Orson. But:
Most states (including Tennessee) have “slayer statutes,” saying that a killer cannot take from a victim if the killing was felonious and intentional. There’s a question here as to whether the killing was felonious; it sounds like self-defense to me. If it WAS felonious, then Chris can’t take and it will pass to Alice’s intestate successors.
Wait a second, or can he? Is he taking from Alice or from Orson? Suddenly I’m blanking on this. I think he’s taking from Alice; she owned in “FEECOS,” as my property prof called it, and Chris would gain nothing from killing Orson, while he would (probably) gain from killing Alice. OK, let’s say he’s taking from Alice.
Let’s also assume Chris killed Alice in valid self-defense, so it’s not felonious and we can keep going.
(Emphasis added.) How old is Chris? Is he over 21 already? If so, he took in fee simple absolute when Alice died, because he was over 21 and not a zombie.
If Chris is not yet 21, then I think the devise would collapse and revert to Orson (again, depending on the legal status of zombies as living, dead, or “other”). The only other option I see is that it could go into constructive trust of some kind until Chris turns 21.
The big question here, of course, is the legal status of zombies. Are they dead? Alive? Some third possibility that’s never existed before? Are they alive, but “new people” (i.e., not retaining the legal identity of the person they originally were)?
The living/dead/undead issue could raise hell with the Rule Against Perpetuities. Can zombies get pregnant? (We know they can bear children because of that horrible scene in the remake of Romero’s Dawn of the Dead, but that gal was already pregnant when she became a zombie. This is a crucial distinction here.)
If zombies can get pregnant, the question is whether they are “alive” legally. If they are legally “dead,” but they can get pregnant, then you could never devise anything to “X’s children,” because the class could be open for more than 21 years after X dies and the Rule Against Perpetuities would kill the devise. (Unless you’re in a USRAP jurisdiction. I don’t think zombies can live for 90 years.)
Another question could arise about competence. Are zombies competent to enter contracts?
Also, if you’re going to give real property to a zombie–say, a favorite nephew of yours who has become undead and thus rather inattentive–you should consider putting it in trust. Zombies don’t seem likely to pay real close attention to what’s going on with their country estates, and would thus be sitting sucks for adverse possessors.