(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.

1. Who is Lars Olsen?
2. Who is leng Thirith?
3. How old is she?
4. What did Lars Olsen say about her?
5. Has she been charged with crimes?
6. Does she have co-defendents?
7. Who are they?
8. Name one of the crimes they are charged with?
9. And another?
10. What country did these things happen in?
11. What is its capital?
12. Which faction or group were the defendents part of ?
13. How long did it last?
14. When did it end?
15. Who was its head?
16. What other name was he known by?
17. Who was Brother Number 2?
18. What did the Khmer Rouge do in 1975?
19. How many Cambodians died?
20. Is brother no 2 one of the defendents?
21. How many women are defendents?

Provide a numbered list of answers.
1. A spokesman for the special U.N. court
2. Former minister of social affairs in the Khmer Rouge regime
3. 78
4. She was "not fit to stand trial as she has dementia."
5. Yes
6. Yes
7. Ieng Sary, Khieu Samphon, and Nuon Chea
8. Crimes against humanity
9. Grave breaches of the Geneva Conventions
10. Cambodia
11. Phnom Penh
12. Khmer Rouge
13. Four years
14. 1979
15. Pol Pot
16. Brother Number 1
17. Nuon Chea
18. Ordered people to work in the countryside.
19. Millions
20. Yes
21. One