What is the evidentiary standard for the son regarding the father's estate?

Primary text

The defendant's statement prevails concerning the negation of the father's estate, supported by his oath. If the defendant denies the father's death, his statement prevails with his oath. The son only needs to swear to the negation of knowledge, as he is negating the action of another, and a father may die without the son knowing. It is sufficient for the son to swear that what he received from his father's estate is insufficient to cover his right, and that he received nothing of it. He is not required to swear that his father left nothing behind, because the father might have left an estate that did not reach him, thereby relieving the son of the obligation to pay from it.