A Brazilian farmer's conviction for hiring the gunmen who killed an American nun and rain-forest defender is a sign of progress for an Amazon state's notoriously corrupt judicial system, lawyers said.

But they said the true test would be whether two ranchers accused of orchestrating Dorothy Stang's 2005 killing will be tried and convicted.

"The most important trials are the ones to come," said Brent Rushforth, a Washington-based lawyer who attended the trial with Stang's brother and sisters. "With the trial of the ranchers the Para state court system can prove impunity is coming to an end."

Courts in Brazil's Amazon traditionally side with the rich and powerful.

In the past 30 years, 772 people have been killed over land disputes in Para state, but only three people alleged to have ordered the killings have gone to trial, according to the Federal Prosecutor's office.

Amair Feijoli da Cunha's conviction Wednesday signals things may be changing.

A jury sentenced Feijoli to 18 years in prison for acting as the middleman between the ranchers who allegedly ordered the 73-year-old nun killed and the gunmen who pumped six shots into her at close range along a muddy jungle road.

The gunmen, Rayfran das Neves Sales and Clodoaldo Carlos Batista, were convicted and sentenced to 27 and 17 years respectively in December — record time in a state where trials can be delayed for years, even decades.

The ranchers, Vitalmiro Moura and Regivaldo Galvao, have managed to avoid trial by taking advantage of the many appeals available under Brazil's legal system.

While it remains to be seen whether authorities will act with the same speed in prosecuting the ranchers, not to mention similar crimes where the victims are poor Brazilians, local lawyers believe that something has changed.

"It was the first case in the history of Para state where they arrested the shooters, the middleman and the masterminds," said Rosilene Socoro Conceicao da Silva, a lawyer for the Catholic Church's Land Pastoral, which helps landless farmers throughout Brazil.

"It's also a landmark in terms of how (quickly) it took to get the first defendants to trial," he added.

The Stang murder trials stand in contrast to the case of Gabriel Pimenta, an activist lawyer killed 25 years ago. The man accused of masterminding that killing is finally set to stand trial next week.

Stang, a native of Dayton, Ohio, spent the last 23 years of her life in this hardscrabble region where she built schools and defended poor settlers, teaching them to defend their rights and respect the rain forest.

Her efforts earned her the enmity of ranchers in a region where hired gunmen routinely evict settlers on the strength of forged land titles.

She lost her life over a patch of forest near Anapu, a muddy town on the Trans-Amazon highway 1,250 miles north of Rio de Janeiro. She wanted to preserve it; Galvao and Moura wanted to cut it down.