In the context of inheritance law (Derecho de sucesiones) causante has a particular meaning that is sometimes overlooked in translation. In its broadest sense (persona de quien otro deriva su derecho), causante is often rendered as “predecessor in title,” a translation that may certainly be appropriate in other circumstances. But in the context of the law of succession, causante more specifically denotes the “deceased” or “decedent.”
Causante has likewise been confused with testador (persona que hace testamento) and translated as “testator,” when the terms are clearly not the same. A causante was obviously a testator if he made a will before his death, but a testador is not a causante until he dies (giving causa or origin to the right to inherit his estate.) In this sense, causante es la persona que por su fallecimiento origina automáticamente la apertura de la sucesión. And of course a causante (“decedent,” “deceased”) was not a testator if he failed to leave a will and, thus, died intestate (murió intestado). In addition to causante, other terms sometimes used to denote a “decedent” or “deceased” include difunto, finado and the Latin expression de cuius.
(Definitions are from the Diccionario Jurídico Colex, Madrid, 2003)