They won't hand over 23-year-old mother-stabber Wang Jiajing to prosecutors until they get the results of his psychiatric tests, Shanghai police said on Sunday.

An economics student at Nihon University in Tokyo for five years, Wang was detained by police on April 1 after stabbing his mother eight times in the chest with a fruit knife at 8:30 pm near the arrivals gate of Pudong International Airport.

The attack had followed an argument over Wang's tuition fees, Shanghai Public Security Bureau said yesterday.

The mother, who has not been fully named by media, denied any such quarrel and insisted her son was in fact disturbed, the Oriental Morning Post reported yesterday.

"Yes, he did ask me why I transferred the money to him so late last month," she told the Shanghai-based paper. "He also said that he was always hearing someone talking to him as if an instrument was installed in his ear."

"He talked about looking for a part-time job in Japan last year but couldn't find one. As prices soared in Japan after the earthquake, I transferred 20,000 yuan (US$3,060) to him, higher than before."

Out of her 7,000 yuan (US$1,071)-a- month salary and 10,000 yuan (US$1,530) borrowed from relatives, the mother had paid between 300,000 yuan (US$45,900) to 400,000 yuan (US$61,200) every year toward her son's tuition and living fees. It was not clear how much her husband, who lives in the US, had paid.

She hoped her son would not be punished.

"We are testing the psychological status of Wang now to see whether he was in an abnormal state of mind at that time," said Lu Feng, a Shanghai Public Security Bureau spokesman, yesterday.

The mother, who gained consciousness after several days in a coma, was transferred to a regular ward from the intensive care unit on Friday last week, said a nurse from the Shanghai Pudong New Area People's Hospital on Sunday.

Her stomach and liver had been damaged but her condition was now stable, the Shanghai paper reported.

Wang would be charged if he intentionally injured another, said a Shanghai Huangpu District Procuratorate Office spokeswoman yesterday, but the family's wishes would also be considered.

"Wang will face punishment under the law as his behavior has endangered a person's life," Wang Yong'er said yesterday. "However, as the person attacked was the suspect's mother, her forgiveness of Wang might make the discipline more lenient."

A sociologist from Fudan University in Shanghai said loneliness played a role.

"The pain of struggling to make a basic living in many developed countries, when not supported by a community or friends or families, can make people lose their minds in the long term," said Gu Xiaoming. "It shows a distortion of his attitude toward life and relationships."