GCPP has been asked in past, what is the difference between a "legally acceptable representative" (used in the EU) and a "legally authorized representative" (used in the U.S.). Per section 1.37 of the ICH E6, "Good Clinical Practice: Consolidated Guidance," a "legally acceptable representative" is defined in as "An individual or juridical or other body authorized under applicable law to consent, on behalf of a prospective subject, to the subject's participation in the clinical trial." ("Legally authorized representative" is defined above.) They are basically synonymous, however; a legally authorized representative is necessary when a subject is not mentally competent to make decisions for him- or herself. Appointment of a legally authorized representative for a mentally incompetent person is governed by applicable state law.

Pour chaque essai clinique, ont été définis des critères de participation (appelés critères d'inclusion). Seules les personnes répondant exactement à ces critères peuvent se porter candidates. Pour une personne mineure ou incapable de consentir, seuls ses parents ou son représentant légal peuvent proposer sa candidature.