Former President Alberto Fujimori went on trial on Monday on human rights charges that could put him in a Peruvian prison for the rest of his life as supporters and critics held rival demonstrations outside the courtroom.
Fujimori, 69, is accused of ordering his security team to carry out two massacres that claimed 25 lives and two kidnappings in the early 1990s, when Peru was battling armed leftist insurgents.
He has denied the charges but faces up to 30 years in prison if convicted. Peru's Supreme Court is hearing the case at a police barracks where Fujimori is being held.
The televised trial is seen by rights activists as a turning point in a country long hobbled by a weak judicial system, impunity for the powerful, and painful memories of a civil war that killed tens of thousands of people.
Dressed in a dark pin-striped suit, Fujimori appeared at turns stoic and angry as he sat alone at a small table before a panel of three Supreme Court judges and scribbled in his notebook while lawyers delivered opening arguments.
Trial and punishment for Fujimori!, read a banner carried by members of Peru's largest union confederation, which had some 200 members rallying to demand Fujimori be convicted.
Fujimori is innocent! Liberty for Fujimori! shouted his supporters, waving orange flags, the color of his Alliance for the Future Party.
His supporters say it is unfair to persecute a man who ended a vicious guerrilla war led by the Maoist group known as the Shining Path and tamed a chaotic economy during his 1990-2000 rule.
Families of victims who disappeared in the two massacres have pushed for the trial for years and are calling for a tough sentence.
Fujimori was extradited to Peru from Chile in September after seven years in exile, five of them in Japan, the country of his parents' birth.
Around 70,000 Peruvians died or disappeared in fighting and massacres between the military, the Shining Path, the Tupac Amaru Revolutionary Movement, and peasants in poor mountain towns during 20 years of conflict that broke out in 1980.
Most were killed before Fujimori took office in 1990, and the violence faded after the capture of the Shining Path's supreme leader Abimael Guzman in 1992.