Prosecutors in the genocide trial of a former Khmer Rouge prison chief demanded a 40-year jail sentence Wednesday for a man they described as responsible for snuffing out innocent lives and spreading terror across Cambodia. Victims of the Khmer Rouge regime called the requested sentence for Kaing Guek Eav unacceptable, with many saying prosecutors should have demanded a life sentence for the 67-year-old former school teacher. Kaing Guek Eav, also known as Duch (pronounced DOIK), 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 1975-79 rule. Some 1.7 million Cambodians died of torture, execution, disease and starvation under the Khmer Rouge, when the Maoist ideologues led by Pol Pot emptied cities and forced virtually the entire population to work on farm collectives. Co-prosecutor William Smith told the court that Duch acknowledged his guilt and had given evidence against other Khmer Rouge leaders. But he said Duch must be held accountable. "The sentence to be imposed by this trial chamber should be 40 years' imprisonment," Smith said, adding that five years had been taken off the request for his cooperation and five more for time already served. "Your honors should be mindful of the dreams and opportunities that were denied, also keep in mind the S-21's unrelenting brutality that was meted out with no mercy to all prisoners including hundreds of children - the most defenseless of victims," he said. "Finally, bear in mind the loss and suffering of the families of the victims who are still suffering to this very day." Duch showed no reaction when the sentence recommendation was read. Soon afterward, he took the stand in the packed courtroom and once again 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. "I acknowledge that I was a member of the Pol Pot force and accordingly I am ... psychologically accountable to the entire Cambodian population for the souls of those who perished," Duch said, adding that he was "deeply remorseful and profoundly affected by the destruction on such a mind-boggling scale." But he also emphasized that he was not alone in carrying out massacres that also took place at 196 death camps across the country and insisted there was little he could do to prevent the killings at S-21. "I could do nothing to help," he said. "Pol Pot regarded these people as thorns in his eyes. Pol Pot really wanted to become a king." Duch is charged with crimes against humanity, war crimes, murder and torture, which carry a maximum penalty of life in prison. Cambodia has no death penalty. He has denied personally killing or torturing the S-21 prisoners, and testified that he acted with reluctance on orders from his superiors, saying he feared for the safely of his family and himself. Khmer Rouge survivors and other Cambodians watching the proceedings expressed a mix of disappointment and outrage at the sentence request. Many also discounted Duch's apology, saying no words could erase the evils he committed. "I cannot accept this sentence request because it is too little," said Chum Mey, 78, one of the few survivors of S-21. "He should get 70 or 80 years. For me, he should be punished by hanging but Cambodian law doesn't allow it." Theary Seng, a Cambodian-American lawyer and rights activist who as a 7-year-old was held in a Khmer Rouge prison with her 4-year-old brother, said there were mitigating circumstances with Duch pleading no contest, offering evidence and expressing some remorse. But she called the sentenced "unacceptable" and said it would create "an uproar among Cambodians." "There are many counts, many crimes he should be found guilty of and each one carries a life sentence," she said. "So even with mitigating circumstances taken into account he should at least get one life sentence, even two or three life sentences." Survivors of S-21 have described how they were routinely beaten, received electric shocks, had their toenails torn out and were waterboarded. Surgeries were performed on detainees without anesthetics. Duch has told the court he is ready to accept heavy punishment for his actions. He is the only accused Khmer Rouge leader to acknowledge responsibility for his actions. Four other senior Khmer Rouge leaders are in custody awaiting trial.