PHNOM PENH, Cambodia - Lawyers for the Khmer Rouge prison chief blamed for thousands of killings in Cambodia accused prosecutors Thursday of making him a scapegoat for all the horrors committed by the regime.

Lawyer Francois Roux also criticized the 40-year jail sentence prosecutors have demanded for Kaing Guek Eav, also known as Duch (pronounced DOIK), as indicative of a prosecution more interested in punishing him than uncovering the truth behind the brutality of the Khmer Rouge's 1975-79 rule.

Duch commanded the notorious S-21 prison where those accused of disloyalty to the xenophobic communist regime were held. He oversaw the torture and execution of about 16,000 men, women and children during the Khmer Rouge's reign.

Some 1.7 million Cambodians died of torture, execution, disease and starvation under the Khmer Rouge, whose Maoist ideologues led by Pol Pot emptied cities and forced virtually the entire population to work on farm collectives.

"As long as the prosecution's submissions make this man a scapegoat, you will not advance the development of humankind one millimeter," Roux told the packed court. "No, Duch does not have to bear the whole horror of the tragedy of Cambodia on his head."

Roux also criticized prosecutors for portraying Duch as a key member of the regime responsible for the network of terror.

"How dare you!" he declared, telling the court that a mere 1 per cent of the Khmer Rouge victims died at S-21.

Duch, 67, is charged with crimes against humanity, war crimes, murder and torture, which carry a maximum penalty of life imprisonment.

Duch has denied personally killing or torturing the S-21 prisoners, and testified that he only reluctantly carried out the orders from his superiors, because he feared for his life and his family's safety.

Addressing the court Wednesday, Duch apologized to the dead, their families, survivors of the regime and to all Cambodians -- something he has done repeatedly since the trial began in March.

He said he was "deeply remorseful and profoundly affected by the destruction on such a mind-boggling scale."

But he emphasized that he was not alone in carrying out torture and killings, which also took place at 196 other prisons across the country, and insisted there was little he could do to prevent the horror at S-21.

"I could do nothing to help," he said. "Pol Pot regarded these people as thorns in his eyes."

The defence team has at times seemed conflicted and desperate to find an angle that might help their client.

Roux has spent much of his time trying to mitigate Duch's role while lawyer Kar Savuth has argued that Duch was not a senior Khmer Rouge leader and therefore should not be prosecuted at all.

"If S-21 did not obey orders, those at S-21 would be identified as enemies by the party," Kar Savuth said Wednesday. "To avoid this, those at S-21 had to do what they were told in order to survive. So Duch is innocent and should be free from prosecution."

Australian co-prosecutor William Smith earlier acknowledged Duch's admissions of guilt and the fact that he has given evidence against other Khmer Rouge leaders, but said he still must be held accountable.

"The crimes committed by the accused at S-21 are rarely matched in modern history in terms of their combined barbarity, scope, duration, premeditation and their callousness," he said. "Not just the victims and their families but the whole of humanity demand a just and proportionate response to these crimes and this court must speak on behalf of that humanity."

Some survivors and other victims of the Khmer Rouge attending the U.N.-backed trial said a 40-year prison term, which would likely lock up Duch for life, would not be harsh enough. They want a life sentence handed down.

"I cannot accept this sentence request because it is too little," said Chum Mey, 78, one of a handful of survivors from the S-21 prison.

Closing arguments are expected to finish Friday. Judges are expected to decide the verdict and sentence by early next year.