Although I have not been able to separate sufficiently from my emotional reaction to this event so as to have an absolutely intellectual response, it would seem that in Beis Din Kipa could not be meted out here.
You see, all Beis Din would have here is:
1. Victim is seen with man on video.
2. Man goes into car and drives.
3. Car is found in front of house.
4. Remains found in freezer.
5. Man’s confession.
The confession is what ties all the points together. However, in Beis Din, a confession is totally invalid as a piece of evidence in a case of personal crime (to exclude monetary cases), let alone in a capital offense. We are used to putting a perp on the witness stand and convicting on the basis of that testimony. In Beis Din this is not admissible. Someone cannot testify about his own personal movements, whether that testimony is in his favour or otherwise.
It is possible that Beis Din could lock him up and throw away the key so as to insure that the public is no longer endangered by his presence, if they ascertain that he is a menace to the public. But to kill him actively or passively on the basis of a confession, it doesn’t seem probable.