There is a new development in the story of an American nun with Colorado ties who was murdered in Brazil in February of last year.

On Wednesday, an Amazon farmer who allegedly ordered her death pleaded guilty. The farmer admitted he arranged the nun's murder because of her campaign to save the rainforest.

Amair Feijoli da Cunha was sentenced to 18 years in prison for his role in the death of 73-year-old Dorothy Stang.

De Cunha said he hired the two gunmen on behalf of two ranchers, who had planned to log a disputed patch of the Amazon rainforest. The two ranchers have been charged with Stang's killing, but legal maneuvering has kept their cases from coming to trial. The two gunmen have already been convicted and were sentenced in December to 27 and 17 years each.

Stang's brother, David Stang, lives in Palmer Lake, Colo. He traveled to Brazil after his sister's death.

"We couldn't ask for anything better," said David Stang. "This is an important piece, but there are still pieces to come. We want the ranchers' appeals to be decided quickly and we want them to stay in jail until they face a jury."

Dorothy Stang was a long-time activist in the Amazon for workers' rights and the environment. Local ranchers and loggers had repeatedly threatened her over the years.

Stang, a naturalized Brazilian originally from Ohio, spent the last 23 years of her life in the remote jungle town of Anapu, some 1,250 miles north of Rio de Janeiro, where she defended the rainforest and poor settlers there.

Stang was shot on a muddy stretch of road deep in the heart of the Amazon following a long-running dispute with ranchers over a patch of forest they wanted to log and then convert into pasture land. She wanted to have the land declared as a sustainable development reserve.

Stang's killing evoked comparisons with rainforest defender Chico Mendes, who was shot in 1988 in the western Amazon state of Acre.

Lawyers for the Stang family said it also was important to convict the men accused of ordering the killing -- something that rarely happens in Para state, where ranchers and loggers are closely linked to politicians and the police.

"Up until now, the history of this region is one of impunity, where the wealthy have their way," said lawyer Brent Rushforth, who flew in from Washington D.C. to attend the trial along with the Stang's brother, David, 63, and her sisters Marguerite Hohm, 73, and Mary Heil, 77.

Outside the courthouse, poor settlers, who traveled for days by bus over washed-out dirt roads, camped out under tarpaulins. Some held banners with Portuguese slogans reading,"Sister Dorothy your blood has cleansed the Earth."

Para is notorious for land-related violence. According to the Catholic Church's Land Pastoral, more than 500 land-related killings have occurred over the past 20 years, but only 10 cases ever went to trial.