Updated

The annulment of the genocide conviction of Guatemala's former U.S-backed dictator and restart his trial halfway through could spawn interminable delays in the effort to see him jailed for the massacre of thousands of Mayans, victims' advocates said Tuesday.

Some said they feared the country's powerful conservative elites had worked behind the scenes to throw the case against Efrain Rios Montt into such chaos that the 86-year-old former general could live the rest of his life under house arrest instead of in prison, or even be freed completely.

Guatemala's top court overturned Rios Montt's conviction late Monday and ordered that the trial be taken back to where it stood on April 19, when a dispute among judges arose over who should hear the case. Rios Montt's defense team said that it was filing a request for his immediate release.

Many victims' advocates saw only a slim possibility of convicting Rios Montt again because of the uncertainty produced by the Constitutional Court's decision. Defense lawyers could, for example, ask for the trial judges to be removed because they already issued a conviction in the case. That could force the trial to start again from scratch, bringing virtually endless possibilities for delay because new judges would not be familiar with much of the evidence.

The Constitutional Court's decision "appears to give us a way forward, but it's a rocky way forward," said Hector Reyes, a lawyer representing victims in the case. "Instead of giving us a way out it creates more judicial complications."

Many in Guatemala said they believe influential business and agricultural leaders pressured the high court to aid the former right-wing dictator for fear his conviction would set a precedent that could lead to further prosecutions for violations of human rights during the civil war. A coalition of business groups has criticized Rios Montt's conviction.

"This is a political decision. The powers-that-be here don't want a trial," said Claudia Samayoa, spokeswoman for a coalition of human rights groups.

On May 10, a three-judge panel convicted Rios Montt of genocide and crimes against humanity for his role in massacres of Mayans during Guatemala's 36-year civil war. The panel found after two months of testimony that Rios Montt, who ruled in 1982-83 following a coup, knew about the slaughter of at least 1,771 Ixil Mayans in the western highlands and didn't stop it.

The tribunal sentenced him to 80 years in prison, drawing cheers from many Guatemalans. It was the first time a former Latin American leader was convicted of such crimes in his home country and the first official acknowledgment that genocide occurred during the war — something the current president, retired Gen. Otto Perez Molina, has denied.

Rios Montt's lawyers immediately filed an appeal, and he spent three days in prison before he was moved to a military hospital, where he remains.

The top court on Monday said it threw out his conviction because the trial should have been stopped while appeals filed by the defense were resolved.

The proceedings, which started in March, had been whipped back and forth ever since April 18, when a Guatemalan judge ordered that the trial should be restarted just as it was nearing closing arguments.

Judge Carol Patricia Flores had been recently reinstated by the Constitutional Court after being removed in February 2012. She ruled that all actions taken in the case since she was first asked to step down were null, which would have sent the trial back to square one.

The next day, April 19, the tribunal hearing the oral part of the trial asked the Constitutional Court to decide if the proceedings should continue.

The trial was suspended for 12 days amid appeals and at times appeared headed for annulment. But it resumed April 30, and 10 days later the tribunal found Rios Montt guilty. It had heard more than 100 witnesses and experts testify about mass rapes and the killings of women and children and other atrocities committed by government troops.

Survivors and relatives of victims had sought for 30 years to bring punishment for Rios Montt. For international observers and Guatemalans on both sides of the war, the trial was seen as a turning point in a nation still wrestling with the trauma of a conflict that killed some 200,000 people.

The defense constantly claimed flaws and miscarriages of justice. Courts ruled on more than 100 complaints and injunctions filed by the defense before the trial even started.