A Guatemala court will begin a special closed-door retrial Monday of former dictator Efrain Rios Montt on charges of genocide and crimes against humanity committed during his 1982-1983 rule.

The 89-year-old will be absent from the trial on grounds of old age and senility -- he is said to be bedridden in his home in a wealthy district of the capital Guatemala City.

Prosecutors hope to reassert a conviction against the ex-general delivered in a May 2013 trial but which was overturned within days by Guatemala's constitutional court, which ordered the new trial. In the discarded verdict he was sentenced to 80 years in prison.

Rios Montt is accused of being responsible for the murders of 1,771 indigenous Mayan Ixils during his reign at the height of Guatemala's 36-year civil war, which ended in 1996.

According to the UN, some 200,000 people died or were made to disappear during the long, brutal conflict.

"We are ready to start the new debate. The witnesses have indicated that they want to come back to testify," Juan Francisco Soto of the Legal Action for Human Rights Center (CALDH), one of the plaintiffs, told AFP.

"If genocide was proved once, we'll be able to prove it in this new trial."

- Political trial? -

The judges hearing the case decided in August to conduct the trial in camera, with no media allowed and only lawyers and relatives of the victims present.

Should he be convicted again, Rios Montt would be subject to detention in line with his health condition, meaning possible hospital internment or home confinement.

He is accused of orchestrating an extermination policy against the indigenous population, which was perceived to be collaborating with the leftwing guerrillas waging war with government forces.

Jaime Hernandez, a defense lawyer for the former dictator, declared "this trial is political."

He stressed to AFP that his client "doesn't understand any imputation made against him -- if there is a conviction or acquittal, he wouldn't know."

Rios Montt, he said, was unable to rise from his bed in his home and was under the care of a nurse. Although he was able at times to speak, he was incapable of fluid communication, the lawyer said.

"There is no reason for this trial to happen," Hernandez added.

The lawyer suggested that the judges involved in the trial were seeking prominence internationally and in front of the section of the Guatemalan population thirsting for the prosecution of military leaders accused of rights violations during the civil war.

Soto rejected that latter point, saying the victims' relatives wanted justice, not revenge.

"The witnesses (in the first trial) were categoric in saying they were there seeking justice so that such acts are never again repeated," he said.

According to CALDH, four of the 100 witnesses from the first trial have since died of age-related illnesses. The testimonies are key in backing nearly 900 pieces of evidence including military documents, reports and expert accounts.

- Other cases -

At the same time as the closed-door case, the same court is meant to conduct a public trial against Rios Montt's former military intelligence chief, Jose Rodriguez.

However, defense and prosecution attorneys are worried that the special nature of the ex-dictator's trial could raise legal complications in that matter.

Soto and Hernandez said they hoped that the judges would clarify the situation to prevent verdicts being subsequently reversed or annulled.

Eighteen other retired military officers have been sentenced for at least 88 massacres committed during the civil war.

Among them is Benedicto Lucas Garcia, the former armed forces chief during the 1978-1982 presidency of his brother Fernando Romeo Lucas Garcia, during whose US-backed rule 93 percent of the atrocities attributed to the military were carried out.

Rios Montt in March 1982 deposed Lucas Garcia, who went on to die in exile in Venezuela in 2006 aged 81 and suffering from Alzheimer's.