(CNN) -- More than three weeks of testimony in the genocide trial of former Guatemalan dictator Efrain Rios Montt were nullified by a judge Thursday on procedural grounds, state-run media reported.
The impact of the ruling on the trial -- which was nearing completion -- was not immediately clear.
A three-judge Supreme Court panel had pushed forward with the trial of Rios Montt despite unresolved objections to procedures in lower courts.
Judge Carol Patricia Flores ruled that because all of the issues at the lower courts had not been settled, the current proceedings are invalid, the state-run AGN news agency reported.
The ruling in effect rewinds the legal process against Rios Montt to where it was in November of 2011, in a pre-trial phase.
Flores called it a regrettable situation, saying the process had come to this point because the proper procedures weren't followed earlier, according to the Network in Solidarity with the People of Guatemala, which had representatives present in the courtroom.
The judge said she was aware that the ruling would not be popular, but that it does not mean that justice will not be done, the group reported.
Standing trial alongside Rios Montt is Mauricio Rodriguez Sanchez, who was head of intelligence in the early 1980s.
The pair are accused of genocide and crimes against humanity. Prosecutors accuse them of ordering 15 massacres between 1982 and 1983 in the northwestern region of Quiche. More than 1,700 Ixil Mayans were killed in those operations, prosecutors say.
Rios Montt ruled Guatemala from 1982 to 1983.
He came to power in a coup and led a military junta while Guatemala was in a bloody civil war between the army and leftist guerrillas. The war did not end until 1996, leaving more than 200,000 people dead and 1 million as refugees.
Prosecutors argued that Rios Montt was aware of the repressive strategies that the military was using against anyone suspected of being a guerrilla, such as killings, forced disappearances and kidnappings.
His defense has argued that he never explicitly ordered the killings of the indigenous group.