( CNN ) -- One of four former Khmer Rouge leaders charged with crimes against humanity was ruled unfit to stand trial and could be set free , a spokesman for the special U.N. court in Cambodia said Thursday . Lars Olsen said the Extraordinary Chambers in the Courts of Cambodia decided that Ieng Thirith , the 78-year-old former minister of social affairs in the Khmer Rouge regime , was `` not fit to stand trial as she has dementia . '' Prosecutors have 24 hours to object to the court 's decision , Olsen said . If there is no objection , Ieng Thirith will be released , he added . Opening statements by the defendants are scheduled for Monday . Ieng Thirith was the only woman among the four defendants in the trial , which charges surviving leaders of the four-year Khmer Rouge regime in the 1970s with crimes against humanity , grave breaches of the Geneva Conventions , genocide , homicide , torture and religious persecution . The other defendants are her husband , Ieng Sary , the former Khmer Rouge foreign minister ; Khieu Samphon , the nominal head of state ; and Nuon Chea , the prime minister , also known as Brother Number 2 . The head of the Khmer Rouge , Pol Pot , was known as Brother Number 1 . He died in 1998 , long before the U.N.-backed court came into existence . Under Pol Pot 's leadership , the Khmer Rouge regime was responsible for the deaths of millions of ordinary Cambodians during a four-year reign of terror that was eventually halted in 1979 by invading Vietnamese forces . In 1975 , the Khmer Rouge ordered people out of Phnom Penh , the capital , and other cities in Cambodia to work in the countryside . It is said to be responsible for about 1.7 million deaths , roughly a quarter of the population at the time . Its stated aim was to create a Communist utopia , but instead the regime forced Cambodians into what has been described as a living hell . City-dwellers were marched into the countryside and forced to work as farm laborers . Those already living in rural Cambodia were expected to produce enough food for the country while teaching farming to those who had never done it before . Currency was abolished , and anyone with an education was considered a threat . No one was allowed modern medicine , and the country isolated itself in an effort to become completely self-sufficient . The results were disastrous : People died of starvation and disease as soldiers tortured and killed anyone suspected of being disloyal . In the end , virtually everyone , including the soldiers , became a target due to the leadership 's paranoia .
The special U.N. court in Cambodia decides Ieng Thirith has dementia . Three others , include Ieng Thirith 's husband , face charges of crimes against humanity . Score: 6