376. The representatives pointed out that the incidents had taken place with the knowledge of the state, “in the context of a counter-subversive military operation planned and executed by agents of the State, with the knowledge of the highest authorities.” The representatives argued, in this regard, that even though the bodies had been removed the day after the operation and the partial selective autopsies had been performed, no investigation was launched to discover whether the use of firearms, and more specifically, the use of lethal force, had been legal. They held, accordingly, that “the State was under obligation to initiate an investigation to clear up the circumstances of the deaths” that occurred as a result of the operation. The representatives emphasized that investigations had not been conducted ex officio even after Hidetaka Ogura made his statements public. According to the representatives, that was the moment when the State acquired a heightened obligation to investigate, because allegations of extrajudicial executions were being made. The representatives added that the investigations began only after January 2, 2001, when APRODEH lodged a complaint about the matter in response to Ogura’s statements, that is, nearly three years after the events had occurred. They therefore argued that the State was responsible for having failed to begin on its own initiative to conduct a conscientious, effective investigation into the reported executions of the alleged victims once it had become aware that they had died as a result of the use of force by agents of the state. 377. The State maintained that it had fulfilled its obligation to investigate the way lethal force had been used by its officials and pointed out that if, as a consequence of these investigations, the State had found that the death of the MRTA fighters had taken place outside the bounds of reasonable and proportional use of force, then investigations would have begun in the interest of clearing up what could have been considered an extrajudicial execution, but that this was not the case. The State explained that the conduct of this first investigation should be distinguished from any differences of opinion or questions about its outcome that had arisen since late 2000 and early 2001, owing to the statements by Hidetaka Ogura, and regarding which the State had also proceeded immediately with an investigation by the public prosecutor specifically to examine the alleged extrajudicial executions. The State held that “any claimed discrepancies, questions or shortcomings as to how the investigations had been conducted upon completion of the [military operation] cannot in and of themselves prove State responsibility.” 378. The State added that “the time to begin examining whether the State fulfilled its obligations to investigate facts considered to be in violation of the [American Convention] should properly be when the State becomes aware of such facts, but not some time years later when someone begins to speculate that such violations may have been committed.” The State invited the Court to “fully assess all the actions the State of Peru had undertaken since 2001 as an immediate response to the complaints brought before the public prosecutor concerning alleged extrajudicial executions of [the three alleged victims].” Considerations of the Court 379. When accusations are made that extrajudicial executions have occurred, it is essential that States conduct an effective investigation into the violation of the right to life recognized in Article 4 of the Convention and determine the responsibilities of all the perpetrators and participants, especially when State agents are involved. 443. 380. The Court has also held that the obligation to investigate does not derive solely from treaty-based provisions of international law binding upon the States Parties, but also from the Cf. Case of Myrna Mack Chang v. Guatemala, supra, para. 156, y Case of the Massacres of El Mozote and surrounding areas v. El Salvador, supra, para. 243. 443