Khieu Samphan told the Extraordinary Chambers in the Courts of Cambodia (ECCC) in Phnom Penh, where he is facing charges of genocide, crimes against humanity and grave breaches of the 1949 Geneva Conventions, that he was merely a nominal head of State with no real powers.
Mr. Samphan, 80, used his opening statement in the trial to deny any responsibility for the atrocities that took place under the Khmer Rouge, which ruled Cambodia from April 1975 to January 1979 and is thought to be responsible for the deaths of as many as two million people.
"From the beginning, the co-prosecutors have conducted guesswork and peremptory claims and generalizations in statements," he said, saying they had relied on anonymous witnesses, books and newspapers to present their case.
"As far as I know, historians, chroniclers and journalists are not judges" They are entitled to be biased, partial, wrong and express opinions freely."
He said he bore no responsibility for the evacuation of thousands of Cambodians from Phnom Penh in 1975, saying this took place before his arrival in the capital.
Mr. Samphan is one of three co-defendants in what is known as Case 002 at the ECCC, a mixed court which was set up under an agreement between the UN and the Cambodian Government. The others are Nuon Chea, the former second-in-command of the Khmer Rouge, and Ieng Sary, the former foreign minister and deputy prime minister.
Mr. Ieng told the ECCC today that he would not testify until the country"s Supreme Court rules on a previous court ruling over a 1996 royal pardon and amnesty. Convicted of genocide while in absentia in 1979, he had been pardoned in 1996.