Rio de Janeiro - A Brazilian judge acquitted estate owner Vitalmiro Bastos Moura in the 2005 murder of US nun Dorothy Stang, in a decision that prompted criticism from legal experts on Wednesday.

"Such oscillations in the judiciary are very bad. One court condemns him to the highest penalty, and another absolves him completely. That difference can, and should, be corrected at the courts," said Cezar Brito, president of the Brazilian Bar Association (OAB).

The verdict was announced late Tuesday, at the end of a two-day trial in the Amazonian city of Belem. The decision overturned the result of a similar trial last year, in which the estate owner known as "Bida" was condemned to 30 years in prison for the murder of the nun in February 2005.

The nun's brother, David Stang, who travelled to Brazil from the United States for the trial, said he was "disappointed" and "surprised" at the verdict, but he vowed to keep fighting "in search of justice."

Bida's acquittal was based on changes in the testimony of a hired killer, Rayfran das Neves Sales, and an estate foreman, Amair Feijoli Cunha, who confessed to having been involved in the murder.

The two men said they killed Dorothy Stang, 74, on their own initiative, and denied that any estate owners had requested that they kill her.

Public prosecutor Edson Souza said he will appeal the decision, while the landowner left Wednesday the jail where he had been kept since May 2007.

"The democratic state forces us to respect this decision, but we will use all legal means to change it," Souza said.

Human rights activists shouted in anger as Judge Raimundo Alves Flexa read the verdict.

The crime that claimed Stang's life caused a stir in Brazil and beyond. The nun was killed on February 12, 2005, in the town of Anapu, in the Brazilian state of Para, where she led a sustainable development project for poor communities and denounced deforestation on the part of local landowners.

Stang belonged to the congregation Notre Dame de Namur and had lived in Brazil for 27 years. She had fought the invasion of land set aside for the poor and for indigenous peoples by estate owners and logging companies.

Estate foreman Feijoli da Cunha has been sentenced to 18 years in jail in connection with the case, while hired killers Neves Sales and Clodoaldo Batista have been sentenced to 28 and 17 years in prison respectively.

Another estate owner charged with planning the murder, Regivaldo Galvao, awaits trial. Human rights activists claim he was the main planner of the nun's death.

The northern Brazilian state of Para has been particularly shaken by violence in the fight for land. In the last 30 years, over 800 small farmers have been killed there, while many activists for the environment and human rights, including several bishops, have complained that they have been followed and received death threats. (dpa)