A case from 1928 would be before the Vatican was an internationally-recognized sovereign state, I think (the treaty with Italy establishing Vatican City was in 1929). Of course earlier there had been the Papal States and the popes between 1870 and 1929 were not treated as subjects of the the king of Italy, I don't think.
Holding the Vatican responsible for the actions of a low-level priest in another country who was violating Catholic ethics by his conduct is a stretch. Was Lyndon Johnson ever put on trial for the My Lai massacre?