Short answer. Not to the depositor himself. Article 1986 provides that once the depositor loses capacity to contract after making the deposit, the thing may be returned only to the person who has the administration of his property and rights — typically a court-appointed guardian, not the incapacitated person and not just any relative.
What the law says
If the depositor should lose his capacity to contract after having made the deposit, the thing cannot be returned except to the persons who may have the administration of his property and rights.
Civil Code, Article 1986 — Depositor Loses Capacity. Read the full provision →
Returning to the wrong hands is not a discharge
The whole point of returning a deposit is to be discharged — to hand the thing back to someone entitled to receive it and be done. Returning it to the wrong person does not achieve that; it can leave you still liable to the person who was entitled, having given the property to someone who was not. That risk is exactly what arises when the depositor has, since leaving the goods, become incapacitated — through illness, injury or age. He looks like the same person you dealt with, but the law no longer treats him as able to give a valid receipt, and handing the thing straight back to him is not a safe discharge.
The thing goes to whoever administers his property
Article 1986 addresses it squarely: If the depositor should lose his capacity to contract after having made the deposit, the thing cannot be returned except to the persons who may have the administration of his property and rights. The thing goes to whoever is legally charged with managing his affairs — ordinarily a guardian of his person or estate appointed by a court, or another representative clothed with authority over his property. The phrase is administration of his property and rights, which points to formal authority to manage assets on his behalf, not merely a family connection or physical proximity to him. That authority is what you are looking for before you release anything.
Not the incapacitated person, not a helpful relative
Two tempting shortcuts are both wrong. The first is returning the goods to the incapacitated depositor because he is, after all, the owner. Ownership is not the issue; capacity to receive and give a valid discharge is, and that is what he has lost. The second is handing the property to a spouse, child or sibling who steps forward. Kinship alone is not administration. A relative may well end up being appointed to manage his affairs, but until someone is actually vested with that authority, releasing the goods to them is releasing them to a stranger for these purposes, and the discharge the article requires has not happened.
Hold the goods and ask for proof of authority
So the safe course is to hold the property and ask for proof of authority before parting with it. What you want to see is the document that shows who administers the depositor's property — a letter of guardianship or an equivalent appointment — and to return the thing to that person against a receipt. If no one has yet been appointed, the goods are better kept than surrendered on trust to whoever asks; the article makes waiting the prudent choice, not an obstructive one. Note the depositor's condition and the date you learned of it, because they explain why you did not simply return the goods on demand.