By Simon Watts
BBC Americas editor
The constitutional court in Guatemala has halted the trial of 16 soldiers charged over one of the worst massacres during the country's civil war.
More than 200,000 people died during the 1960-96 civil war
The court went against legal precedent in Guatemala by ruling that a 1996 amnesty law covered massacre cases.
Human rights groups have called the decision disastrous.
More than 200 people died in 1982 when a commando unit from Guatemala's army burst into the village of Dos Erres, searching for guerrilla sympathisers.
A United Nations report on the massacre said the commandos raped local women and used hammers for some of the killings.
Now, after 23 years, the constitutional court has unexpectedly thrown out the case against the troops.
Until now, the Guatemalan judiciary had interpreted the country's amnesty provisions as not applying to massacres.
Human rights campaigners immediately voiced alarm about the impact of this decision on the investigation of other atrocities.
Coming from the highest court in the land, it is an important precedent, but the same legal issues are being considered by other courts, and there are likely to be appeals.
More than 200,000 people are estimated to have died during the 36-year civil war.
The powerful Guatemalan army - backed by the US - fought a vicious campaign to eliminate Marxist guerrillas from the mainly indigenous countryside.