Legal Question in Real Estate Law in California

That will turn on the specific facts of the situation.

If someone's negligence caused the injury (using the term "caused" in the sense of legal proximate cause of the injury) that person may be liable. Someone is negligent if they fail to do something, or do something, that they have a legal duty to do, or to refrain from doing. A former owner, after close of escrow, might still have some duties with respect to the occupants of a property. Closing a sale does not necessarily wipe out all duties. Nevertheless, the more remote a person's connection with a property has become, the less likely the person is to be found negligent. It all depends upon what happened is a particular case, and there is no real cut-and-dried rule about former owners vs. new owners. The jury and/or the judge will decide.

If you're asking who is the owner of the property for the purposes of premises liability, then arguably the buyer is the owner of the property upon close of escrow. A hold over creates a tenancy, not a form of ownership.

With that said, there would still be issues such as causation and negligence to prove liability.