(Adds church statement, paragraph 11)
By Hilary Burke
LA PLATA, Argentina, Oct 9 (Reuters) - A former police chaplain was sentenced to life imprisonment on Tuesday for involvement in torture, kidnapping and murder during Argentina's "dirty war," in the first trial of a clergyman for rights abuses under military rule.
Roman Catholic priest Christian Von Wernich tended to the notorious Buenos Aires provincial police force, and rights lawyers say he pressured torture victims to talk during visits to clandestine detention centers.
Outside the court in the central city of La Plata, crowds cheered and set off firecrackers as the verdict was read in the televised trial.
"It's a historic day, a wonderful day ... it's something we mothers didn't think we'd live to see," said Tati Almeyda, of the Founding Line of the Mothers of the Plaza de Mayo, wearing the white headscarf that has become a symbol for human rights campaigners worldwide.
"Justice has been done. The Catholic Church was an accomplice," she added.
The mothers of murdered political activists have led efforts for human rights convictions related to the dirty war, when thousands of leftist dissidents were systematically maimed and killed during Argentina's 1976-1983 dictatorship.
Von Wernich, 69, sat with his head hanging low, his mouth turned downward and his arms crossed over a bulletproof vest during sentencing for the offenses, which one of the judges described as crimes against humanity.
When he was given a chance to speak hours before the verdict was announced, Von Wernich cited the Bible and said firmly: "If we want to reach the truth, we should do it peacefully ... because a heart filled with malice is a heart that doesn't understand what God wants and what man needs: reconciliation."
Although Von Wernich did not testify during the three-month trial, he told court officials previously he was unaware that detainees were being tortured or held illegally.
One of Von Wernich's defense lawyers said the charges against his client were excessive and suggested the case was an ideological attack against the Catholic Church.
Following the verdict, Argentina's Catholic leaders issued a statement saying the Church was saddened "by the pain of a priest's participation in these very grave crimes."
Many rights activists accuse the Church hierarchy of supporting the military dictatorship and opting to keep silent about its brutality.
Von Wernich's trial was the first case to probe dirty war-era crimes since a former provincial police commissioner was sentenced to life in prison in September 2006.
That trial was marred by the disappearance of a key witness, Jorge Julio Lopez, who has not been seen since and whom many fear may have been abducted and killed.
Center-left President Nestor Kirchner persuaded Congress to scrap amnesty laws shielding rights abusers from prosecution for dictatorship-era crimes, and the Supreme Court ruled in the same vein in 2005.
That paved the way for new and reopened investigations into the deaths and disappearances of between 11,000 and 30,000 people during the dirty war purge of leftists, which also swept up Argentines who were not involved in politics.
(Additional reporting by Miguel Lo Bianco)