16 BOUYID v. BELGIUM JUDGMENT physical force which had not been made strictly necessary by the person’s own conduct diminished human dignity and was in principle an infringement of the right set forth in Article 3. It further referred to the principle that in order for ill-treatment to fall within the scope of Article 3 it had to attain a minimum level of severity. Furthermore, some forms of violence, although they might be condemned on moral grounds and also very broadly under the domestic law of the Contracting States, would not fall within Article 3. The Chamber further noted that the Government had disputed the fact that the applicants had been slapped by police officers, and had submitted that the medical certificates provided did not establish that the injuries recorded had been caused by such slaps. It nevertheless found it pointless to rule on the veracity or otherwise of the applicants’ allegations, considering that, even supposing that they were proved, the acts complained of by the applicants would not, in the circumstances of the case, constitute treatment in breach of Article 3 of the Convention. The Chamber concluded as follows (§ 51): “... [E]ven supposing that the slapping took place, in both cases it was an isolated slap inflicted thoughtlessly by a police officer who was exasperated by the applicants’ disrespectful or provocative conduct, without seeking to make them confess. Moreover, there was apparently an atmosphere of tension between the members of the applicants’ family and police officers in their neighbourhood. In those circumstances, even though one of the applicants was only 17 at the time and whilst it is comprehensible that, if the events really took place as the applicants described, they must have felt deep resentment, the Court cannot ignore the fact that these were oneoff occurrences in a situation of nervous tension and without any serious or long-term effect. It takes the view that acts of this type, though unacceptable, cannot be regarded as generating a sufficient degree of humiliation or debasement for a breach of Article 3 of the Convention to be established. In other words, in any event, the abovementioned threshold of severity has not been reached in the present case, such that no question of a violation of that provision, under either its substantive or its procedural head, arises.” B. The parties’ submissions 1. The applicants 57. As regards the substantive aspect of Article 3, the applicants complained that the Chamber had departed from the principles established by the Grand Chamber. They submitted that the Chamber had omitted to apply the presumptions of causality and severity involved in cases of violence against persons who had been deprived of their liberty or were under the control of the police. In such cases there was a presumption of a causal link between the marks left by blows and their imputability to the police, which could be rebutted by reasonable explanations from the alleged perpetrators. If that was not the case, the second presumption came into play where the victim was deprived of his or her liberty: since the use of physical