The facts of the case relate to the extrajudicial execution of 15 people, who were residents in the Barrios Altos neighborhood in Lima city, by 6 heavily armed individuals. Upon entering the place, the attackers fired indiscriminately, they then fled the scene in 2 vehicles. Judicial investigations and journalist reports revealed that those responsible worked for military intelligence and were members of the Peruvian army who served in the Colina Group.

Despite the fact that the events took place in 1991, the judicial authorities only opened a serious investigation into the incident in April 1995, which was interrupted by a complaint of competence from the military court presented before the High Court for the reason that the events related to military personnel in active service. Before the Court could resolve the matter, the Congress passed an Amnesty law, which exonerated military personnel, police and civilians of responsibility, who had committed or participated in human rights violations between 1980 and 1995. The effect of this law was to determine the definitive closing of judicial proceedings and thereby avoid criminal responsibility for those responsible for the massacre.

The IA Court declared that the Amnesty law was incompatible with the American Convention.