- Subject who could be regarded as "vulnerable" according to International Conference on Harmonisation (ICH) Good Clinical Practice (GCP) guidelines (e.g., the subject's willingness to volunteer in a clinical trial may be unduly influenced by the expectation, whether justified or not, of benefits associated with participation, or of a retaliatory response from senior members of a hierarchy in case of refusal to participate, plus persons kept in detention; persons in nursing homes; subjects in emergency situations; homeless persons; and nomads)