A rancher goes to trial Monday for the killing of an American nun whose death while trying to save the Amazon rain forest now threatens to strip away the impunity of the region's often violent elite...``If Moura is convicted, ranchers will think twice before ordering this kind of killing,'' said Jose Batista Afonso, a lawyer with the Roman Catholic Church's Land Pastoral, which defends the land rights of the poor. Over the past 30 years, 1,237 rural workers, union leaders and activist have been killed in Brazilian land disputes.