BOUYID v. BELGIUM JUDGMENT 31 112. Given that the applicants referred only to minor bodily injuries and did not demonstrate that they had undergone serious physical or mental suffering, the treatment in question cannot be described as inhuman or, a fortiori, torture. The Court therefore finds that the present case involved degrading treatment. 113. Accordingly, there has been a violation of the substantive head of Article 3 in respect of each of the applicants. 2. Procedural aspect of the complaint (a) General principles 114. The Court refers to the general principles set out, inter alia, in El-Masri (cited above, §§ 182-85) and Mocanu and Others (cited above, §§ 316-26). 115. Those principles indicate that the general prohibition of torture and inhuman or degrading treatment or punishment by agents of the State in particular would be ineffective in practice if no procedure existed for the investigation of allegations of ill-treatment of persons held by them. 116. Thus, having regard to the general duty on the State under Article 1 of the Convention to “secure to everyone within [its] jurisdiction the rights and freedoms defined in [the] Convention”, the provisions of Article 3 require by implication that there should be some form of effective official investigation where an individual makes a credible assertion that he has suffered treatment infringing Article 3 at the hands, inter alia, of the police or other similar authorities. 117. The essential purpose of such an investigation is to secure the effective implementation of the domestic laws prohibiting torture and inhuman or degrading treatment or punishment in cases involving State agents or bodies, and to ensure their accountability for ill-treatment occurring under their responsibility. 118. Generally speaking, for an investigation to be effective, the institutions and persons responsible for carrying it out must be independent from those targeted by it. This means not only a lack of any hierarchical or institutional connection but also practical independence. 119. Whatever mode is employed, the authorities must act of their own motion. In addition, in order to be effective the investigation must be capable of leading to the identification and punishment of those responsible. It should also be broad enough to permit the investigating authorities to take into consideration not only the actions of the State agents who directly used force but also all the surrounding circumstances. 120. Although this is not an obligation of results to be achieved but of means to be employed, any deficiency in the investigation which undermines its ability to establish the cause of injuries or the identity of the