General Rios Montt's attempts to trip up the president may yet inspire a backlash.
Gen Rios Montt's former chief of military intelligence, Gen Jose Mauricio Rodriguez Sanchez, is on trial alongside the ex-leader.
But Gen Rios Montt was cleared of manslaughter charges in 2006, with prosecutors citing a lack of evidence.
Gen Rios Montt's lawyers have argued he was not responsible for the alleged crimes "since he was never on the battlefield".
That kind of comment worries those who think that General Rios Montt would keep Mr Portillo under the army's thumb.
ECONOMIST: Guatemala��s democracy of chickens, rabbits��and locals
Then-U.S. President Ronald Reagan went as far as to say that Rios Montt was being given a "bum rap" by critics.
On the mainland, the glacier-covered cone of the Cerro Macau volcano peeked above the cloud and the straggly fishing port of Puerto Montt came into view.
Matamoros prison, where Rios Montt is now behind bars, is located on a military base in Guatemala City where the former general spent time as a young cadet.
Perez Molina's name was brought up during the trial when a former soldier accused him of ordering executions while serving in the military in the Rios Montt regime.
But some are wondering if Rios Montt can successfully appeal.
General Rios Montt returned to the political limelight when he ran for president in 2003, despite a constitutional rule that no-one who had overthrown a government could stand for the presidency.
"He is not comfortable, but as a good soldier he is used to this, " said Rios Montt's lawyer, Francisco Palomo, who is expected to seek to have the ex-general transferred to a hospital or to have his sentence be served under house arrest.
But if the United States deserves criticism for openly supporting Rios Montt's rule, it also should be credited for supporting Guatemalan efforts to put the former dictator on trial, said Anita Isaacs, a professor of political science at Haverford College whose research focuses on Guatemalan politics.
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