GUATEMALA CITY, May 20 (Reuters) - Guatemala's constitutional court on Monday overturned a genocide conviction against former dictator Efrain Rios Montt, throwing out all proceedings in his case since a dispute broke out last month over who should hear it.

Rios Montt was found guilty on May 10 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 dating back until April 19. It was then that the trial against Rios Montt was suspended after a spat between judges over who should take the case. (Reporting by Mike McDonald; Editing by Dave Graham)

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