XIX, Guatemala — Tiburcio Utuy thought he saw fear cross the former dictator’s face.

A judge had just ruled that the military dictator, Gen. Efraín Ríos Montt, now 86, should stand trial for genocide and crimes against humanity committed under his rule in the 1980s, a decision Mr. Utuy and other Maya survivors of Guatemala’s 34-year civil war had gathered in the courtroom to hear in person.

“He won’t suffer the same way we suffered — but he will be scared,” Mr. Utuy said in his mountaintop village a few days after the ruling in late January. “And maybe he will spend a little bit of time in prison.”

Mr. Utuy, 71, is set to be a witness in a trial that few believed would ever take place.

But Guatemala’s justice system has begun a transformation. In a show of political will, prosecutors are taking long-dormant human rights cases to court, armed with evidence that victims and their advocates have painstakingly compiled over more than a decade — as much to bear witness as to bring judgment.

“It’s sending the most important message of the rule of law — that nobody is above the law,” said Claudia Paz y Paz, the attorney general, who many here say has been one of the most important forces behind the change.