An appeals court in Mexico has found that there is insufficient evidence to prosecute former Mexican president Luis Echeverria in the 1968 mass killings of student protesters in Mexico City’s Tlatelolco Square. Echeverria was the head of the federal police at the time of the massacre.

Federal agents fired on a peaceful pro-democracy protest in Tlatelolco Square on the evening of October 2, 1968, days before the start of the Mexico City Olympics. Five thousand students and others were participating in the rally, and estimates of the number of dead range into the hundreds. (The official government tally was just thirty.)

The killings provoked an appalled response from Mexico’s citizens, and helped to spur a new resistance to the country’s repressive government. Mexico’s current president, Ernesto Zedillo, has called 1968 “the watershed of the country’s political life, when a real public outcry began for a more democratic country.”

Echeverria served as president of Mexico from 1970 to 1976. Since 2006 he had been held under house arrest in connection with the Tlatelolco Square killings.

A statement from Amnesty International yesterday called the court’s ruling “a symptom of the failure of successive Mexican governments and legislatures, as well as the courts and prosecutors, to live up to Mexico’s international human rights commitments.”