Short answer. Article 393 of the Civil Code places the burden squarely on the person asserting the claim. Whoever wants a right belonging to a missing person must prove that the missing person was alive at the critical moment — the existence of that person cannot simply be assumed.
What the law says
Whoever claims a right pertaining to a person whose existence is not recognized must prove that he was living at the time his existence was necessary in order to acquire said right.
Civil Code, Article 393 — Proving Existence to Claim. Read the full provision →
The claimant bears the burden of proof
Article 393 imposes the burden on the person making the claim. If you want to assert a right that would flow through a missing or absent person — for example, a right to inherit property that the absent person should have received — you must prove that the absent person was alive at the specific moment their existence was legally necessary. You cannot argue in the abstract that the person might have been alive, or rely on absence of proof of death. The burden is yours to discharge with positive evidence.
What the critical moment means
The phrase 'at the time his existence was necessary' is precise. It refers to the legal moment when the absent person's being alive mattered for the right to arise. In succession, this is typically the moment of the decedent's death — the missing heir must have been alive at that instant for the inheritance right to vest. In other situations, the critical moment depends on the nature of the right being claimed. Proving survival for the wrong moment does not satisfy Article 393; the proof must correspond to the legally relevant point in time.
Why this rule matters when an estate has missing heirs
When settling a deceased person's estate, questions about a missing heir can hold up distribution or alter who gets what. If one sibling is missing and another wants to claim that sibling's share as well — arguing the sibling predeceased the decedent and that the right of representation applies — Article 393 requires actual proof. Without evidence that the missing person had already died before the decedent, the claim cannot simply proceed on an assumption. The burden is not easily met, and the standard applies rigorously because the stakes involve other heirs' interests.
This rule and the presumption of absence
Article 393 operates alongside the Civil Code's provisions on presumptive death. Those provisions establish periods after which a missing person is presumed dead for certain purposes. Article 393, however, addresses a different situation: someone is claiming a right through an absent person, and that claim requires proof of the person's existence at a particular time. The absence of a judicial declaration of death is not enough — the person making the claim must still produce affirmative evidence. If you are involved in an estate dispute where a missing heir's status is in question, the application of this burden rule is one of the first things to assess.