Short answer. Yes. Rule 102, Section 3 of the Rules of Court allows the petition to be signed and verified by the detained person or by some person on his behalf — which includes a relative. It must state who is restrained, by whom and where, and attach the commitment papers or allege that the detention has no legal authority.
What the law says
Application for the writ shall be by petition signed and verified either by the party for whose relief it is intended, or by some person on his behalf
Rule 102, Section 3 — Requisites of application therefor. Read the full provision →
What the law says
if the imprisonment or restraint is without any legal authority, such fact shall appear
Rule 102, Section 3 — Requisites of application therefor. Read the full provision →
Who may sign the petition
The rule is deliberately generous about who files. The application shall be by petition signed and verified either by the party for whose relief it is intended, or by some person on his behalf. A person locked in a detention cell usually cannot draft, sign and file anything, so the Rules let someone outside do it for him. The section imposes no requirement of kinship — some person on his behalf is any person acting for the detainee — so a spouse, parent, sibling or child certainly qualifies. What the filer cannot skip is verification: the petition is sworn, so whoever signs attests to the truth of its allegations.
The four things the petition must set forth
Section 3 lists the required contents. First, that the person in whose behalf the application is made is imprisoned or restrained of his liberty. Second, the officer or name of the person by whom he is so imprisoned or restrained. Third, the place where he is so imprisoned or restrained, if known. Fourth, a copy of the commitment or cause of detention if it can be procured without impairing the efficiency of the remedy — or, where the restraint has no legal basis at all, an allegation to that effect, because if the imprisonment or restraint is without any legal authority, such fact shall appear.
What if you do not know who is holding them
Families of a person taken into custody often cannot name the exact officer responsible, and the rule anticipates that. If the officer and the detaining person are unknown or uncertain, such officer or person may be described by an assumed appellation, and the person who is served with the writ shall be deemed the person intended. In plain terms: you may name the custodian descriptively, and whoever actually receives the writ is treated as the respondent. So uncertainty about names is not a reason to delay filing. State what you know — the place if known, the circumstances of the restraint — and let service of the writ fix the rest.
Keep the petition focused on the detention
Habeas corpus under Rule 102 is aimed at one thing: testing whether a person's imprisonment or restraint of liberty is lawful. The petition should therefore be built around the fact of restraint, the custodian and the place — not around grievances the writ does not answer. Before filing, gather what Section 3 asks for: any commitment order, arrest documents or paperwork showing the cause of detention, or, if the family was shown nothing, be prepared to allege that the restraint is without legal authority. A lawyer will also want the timeline of the arrest or pick-up and where the person was last seen or held.