84 GIULIANI AND GAGGIO v. ITALY JUDGMENT examinations impossible, was authorised at the applicants' request (see paragraph 49 above). 320. The Court also notes that the procedural obligations arising out of Article 2 require that an effective “investigation” be carried out and do not require the holding of public hearings. Hence, if the evidence gathered by the authorities is sufficient to rule out any criminal responsibility on the part of the State agent who had recourse to force, the Convention does not prohibit the discontinuation of the proceedings at the preliminary investigation stage. As the Court has just found, the evidence gathered by the prosecuting authorities, and in particular the footage of the attack on the jeep, led to the conclusion, beyond reasonable doubt, that M.P. had acted in self-defence, which constitutes a ground of justification under Italian criminal law. 321. Furthermore, it cannot be said that the prosecuting authorities accepted without question the version supplied by the law-enforcement officers implicated in the events. They not only questioned numerous witnesses, including demonstrators and third parties who had witnessed the events on Piazza Alimonda (see paragraphs 45-46 above), but also ordered several forensic examinations, including an expert medical examination and three sets of ballistics tests (see paragraphs 48-50 and 54-62 above). The fact that the experts did not agree on all aspects of the reconstruction of events (and, in particular, on the distance from which the shot had been fired and the trajectory of the bullet) was not, in itself, such as to make further investigations necessary, given that it was for the judge to assess the pertinence of the explanations given by the various experts and whether they were compatible with the existence of grounds of justification exempting the accused from criminal responsibility. 322. It is true that the carabinieri, that is, the armed force to which M.P. and F.C. belonged, were given the task of conducting certain checks (see paragraph 290 above). However, in view of the technical and objective nature of those checks, this fact cannot be said to have adversely affected the impartiality of the investigation. To hold otherwise would be to impose unacceptable restrictions in many cases on the ability of the courts to call on the expertise of the law-enforcement agencies, which often have particular competence in the matter (see, mutatis mutandis and from the standpoint of Article 6 of the Convention, Emmanuello v. Italy (dec.), no. 35791/97, 31 August 1999). In the instant case, the law-enforcement agencies were already present at the scene and were thus able to secure the area and search for and record any items of relevance to the investigation. Given the number of people on Piazza Alimonda and the confusion reigning after the shots were fired, the authorities cannot be criticised for not finding objects as small as the bullets fired by M.P. 323. In the Court's view, Mr Romanini's appointment as an expert raises some more delicate issues, as he had openly defended the view, in an article