Colombia’s Supreme Court is calling on powerful former President Álvaro Uribe to testify in an investigation into three massacres that could once and for all establish whether he had any ties to violent paramilitary groups.

The new legal quandary for Uribe is potentially more damaging than a separate Supreme Court probe into possible witness tampering that sparked protests earlier this month after magistrates placed the ex-president on house arrest.

Details of the massacre inquiry are contained in a 71-page court document obtained by The Associated Press on Sunday and also published in local media in which magistrates examine whether Uribe had any connection to three mass killings in the Antioquia department as well as the death of a human rights activist during his time as governor.

Both cases strike at long-standing — but never legally proven — accusations that Uribe had a direct role in paramilitary groups, which were formed by landowners during Colombia’s long civil conflict to fight violent Marxist guerrillas.

Though the Supreme Court is still in an investigative stage, the inquiries have split open tensions in Colombia over the peace process that led to an accord with the country’s biggest rebel movement. Uribe has vehemently denied the accusations and his lawyer is calling into question the timing of the new court request. Human rights activists, meanwhile, have praised the court for advancing the probes in a country where the powerful routinely escape accountability.