By Mike McDonald
Rios Montt, 86, was found guilty on May 10 of overseeing the killings by the armed forces of at least 1,771 members of the Maya Ixil population during his 1982-83 rule. He was sentenced to 80 years in prison.
However, in a ruling on Monday, the country's Constitutional Court ordered that all the proceedings be voided going back to April 19, when one of the presiding judges suspended the trial because of a dispute with another judge over who should hear it.
It was unclear when the trial might restart.
For more on Rios Montt, see Rios Montt Found Guilty of Genocide and Guatemalan Strongman Charged with Genocide.