The former Cambodian Khmer Rouge prison chief Duch, who was convicted of crimes against humanity, will appeal against his sentence, his lawyer has said.
Duch, 67, whose full name is Kaing Guek Eav, was sentenced to 35 years in prison by a UN-backed court on Monday.
He was found guilty of overseeing the torture and execution of thousands of people at the notorious Tuol Sleng prison in Phnom Penh.
His lawyer gave no further details of the grounds for the appeal.
Duch was the first of five surviving senior Khmer Rouge figures to go on trial.
He had admitted his role in the killings and torture of thousands of men, women and children at the prison, but said he was following orders and had asked the court to acquit him.
He is expected to serve 19 years in prison, because of a reduction for time already served.His lawyer, Kar Savuth, told the AFP news agency: "We will appeal against the decision."
A spokesman for the tribunal said the lawyer had indicated soon after the verdict was given that an appeal would be launched.
"He said he would have appealed a sentence of even one day," said Reach Sambath.
Up to two million people died because of the policies of the Khmer Rouge, which ruled Cambodia from 1975-1979.
Only about a dozen people who were held at Tuol Sleng are thought to have survived, three of whom are still alive. Up to 17,000 people are believed to have died there.