The original programmer(s) probably w(as/ere) responsible...
Just FYI, it's perfectly feasible -- and generally accepted in the genre -- that AI would be an emergent system, and thus there wouldn't really be any particular responsibility on the part of the initial programmer, any more than a parent is responsible for the actions of a child (including a grown child).
Re: Speculation...
Just FYI, it's perfectly feasible -- and generally accepted in the genre -- that AI would be an emergent system, and thus there wouldn't really be any particular responsibility on the part of the initial programmer, any more than a parent is responsible for the actions of a child (including a grown child).