Leung was deemed unfit to plead until May 5, 2010 - a year after the killing at their home at Lok Man Sun Chuen, Hung Hom. She admitted bashing Tsui to death but disputed the cause of the killing.

During the examination, Leung recalled that Tsui had scolded her before the killing. Her mother said that she would be a demonic girl in the next life and that she was 'no good'. Tsui purportedly grabbed a hammer and Leung believed that her mother was going to hurt her.

Tsui chased Leung around the flat, Yu told the court. Tsui grabbed Leung's clothes and Leung hit her with a hammer 10 times. The defendant also said Tsui tried to choke her. Leung was not injured in the attack, prosecutor Walter Lau said.

'She told me her mother had been possessed by ghosts for a long time,' Yu said. Based on medical records, it was highly probable that Tsui suffered from schizophrenia.

Psychiatrist Dr Amy Liu told the court that that Leung thought her mother was about to kill her during a relapse in her condition.

The defendant also tried to convince Yu that her mother possessed extraordinary powers. Tsui had a red mark on her forehead for some time, that looked like a talisman, Leung said during her examination. However, senior medical officer of the Department of Health, Dr Poon Wai-ming, who carried out an autopsy on the deceased, testified that the purported red mark was absent.

Poon said that the injuries inflicted on Tsui could have been caused by more than 100 hammer blows. The attack could have been carried out by someone 'out of control', Poon said. But he could not comment whether it was a 'frenzy attack', as put to him by defence counsel, Michael Arthur.

Leung denied she suffered from schizophrenia that was first diagnosed in the 90s. But she believed she was severely depressed, Yu said.

The trial continues today before Mr Justice Michael McMahon.