Guatemala’s constitutional court has overturned a genocide conviction against former dictator José Efraín Ríos Montt, throwing out all proceedings against him since a dispute broke out in April over who should hear it.

Ríos Montt was found guilty on 10 May of overseeing the deliberate 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.

But the constitutional court said it had thrown out all proceedings in the case that took place after 19 April. It was then that the trial against Ríos Montt was suspended after a spat between judges over who should take the case.

Constitutional court secretary Martin Guzman said the trial needed to go back to where it stood on 19 April to solve several appeal issues.

A three-judge panel convicted the 86-year-old of genocide and crimes against humanity in what was regarded as a historic decision involving a Latin American leader.

His lawyers immediately filed an appeal and he spent only one day in prison before he was moved to a military hospital, where he remains.