The lawyer for the only female Khmer Rouge leader facing genocide charges in Cambodia's U.N.-backed war crimes tribunal says her client has dementia and should not be put on trial.

Defense attorney Diana Ellis on Thursday told the court in Phnom Penh that 79-year-old defendant Ieng Thirith has, in the lawyer's words, “no ability to recall events in her life… ,” and as such “should be found unfit to stand trial.”

Mental health experts told tribunal judges Wednesday that the former Khmer Rouge social affairs minister had serious health issues that could prevent her from standing trial. It was not immediately clear when the court will rule on the motion.

Ieng Thirith faces an array of charges, including crimes against humanity and war crimes in the deaths of up to 2 million Cambodians during Khmer Rouge rule. The other defendants are nominal Khmer Rouge head of state Khieu Samphan, reputed chief ideologue Nuon Chea and Ieng Thirth's husband, Khmer Rouge Foreign Minister Leng Sary.

Khmer Rouge leader Pol Pot died in 1998.

Earlier this week, the tribunal said trial proceedings against the four defendants would begin November 21.

The tribunal began hearing preliminary motions in the case in June. Last month, it decided to speed up proceedings by dividing the complex charges into segments. A court spokesman at the time said the decision to split the charges means the court will hand down separate verdicts on each charge as the trial proceeds.

Observers had complained that it could take as long as a decade to reach a single verdict, if all of the charges were tried at once. All the defendants are already elderly and there is some doubt whether all would live that long.