When police told 70-year-old Yu Hongzhi that his only son had died in one of their detention centres, they said that a hole had appeared in his heart after they cleaned a pimple. Disbelieving, Yu demanded an autopsy and the video of the interrogation.
'Thirty seconds of the video was missing,' he said. 'He was normal before that, but acted as if he was in great pain afterwards.'
The autopsy report on March 17 by a department of the Ministry of Justice found that Yu's heart had fatal injuries caused by a needle-like instrument.
'Who used this instrument and stabbed it into my son's heart?' Yu said. 'He was very healthy and had no psychological problem. I see no reason why he would kill himself.'
The death of Yu Weiping was one of at least 10 abnormal deaths in detention centres run by the Ministry of Public Security over the past 14 months. They have sparked an intense debate over whether these centres should be run by the police or handed over to an institution independent of the ministry and responsible to the Ministry of Justice.
While the Ministry of Public Security does not publish the number of detention centres, scholars estimate the figure at more than 3,000 across China, holding at least 800,000 people a year for a limited period before they go to trial.
The debate pits lawyers, scholars and reformists in the Ministry of Justice against the Ministry of Public Security, one of the most powerful institutions in China, which opposes any change to the status quo.
Last August, Yu Weiping was detained as a suspect after a death at a dance club in Weihai , Shandong province, of which he was co-owner; the death followed a fight on the premises. He was held at a detention centre in Rushan and found dead by other inmates on November 13.
'The video shows nobody in the detention centre showing any concern for his pain,' his father said. 'He is my only son and I felt that my world was collapsing.'
Just before 7am on April 7, an inmate found the body of a fellow prisoner named Xue in a basin in the yard of a detention centre in Gongan county, Jingzhou city , Hubei province. The basin, used for washing clothes, was just 46cm deep. Police said Xue had drowned and cremated his body the next day.
Xue, 55, had been detained on March 27 for stealing a bicycle from a supermarket; he was fined 1,000 yuan (HK$1,135) and had served 15 days in the centre.
While his family accepted the explanation of his death and a substantial payment, believed to be 200,000 yuan, many netizens did not. 'Is it a basin or a swimming pool we are talking about?' one of them asked.
Other unlikely explanations given by the police for centre deaths include hanging by shoelaces or underwear, falling to death in the toilet and drinking boiling water during interrogation.
The public anger reached such a point that Meng Jianzhu , minister of public security, was forced to respond publicly last month.
'Recently, unnatural deaths occurred successively in certain places,' he said. 'This has seriously harmed the public's confidence in law enforcement by police authorities.'
What many suspect is that these inmates died a violent death at the hands of the police or other inmates.
On February 12 last year, Li Qiaoming , 24, died at a detention centre in Jinning county, Yunnan province. Police said he banged his head against a wall during a game of hide-and-seek with other detainees. An investigation by the prosecutor found he had been beaten to death by three other inmates.
On February 16 this year, Chen Xujin died at a detention centre in Xiushui county, Jiujiang city , Jiangxi . Police said Chen collapsed and died suddenly in the toilet. An autopsy showed that his heart and liver had ceased to function because of long-term illnesses; his family believed he was beaten to death. The director of the centre was suspended from duty.
In one case in Yantai , detention served as a way to force a businessman to give up 46 million yuan in compensation. Qiu Zhaoxuan , the head of a silk company, was detained in the city's detention centre for 21 months from December 2006.
Over many years, he had built up a silk printing factory that was in 2005 officially estimated to be worth 70 million yuan. That July, a local developer signed an agreement with Qiu to buy the land and demolish the factory for a fee of 63 million yuan. Qiu was then charged with fraud, sentenced to 15 years in prison and held in the centre.
After months of negotiations, he agreed to a reduced compensation of 17 million yuan; the next day he was released from the centre and the 15-year sentence was quashed.
Chen Minggui, a Hong Kong consultant, said police used inmates in prisons and detention centres to report on each other. 'If you provide new and useful information, you have the hope of your sentence being reduced. This produces an atmosphere of mistrust and suspicion among the prisoners and makes them easier to control. Everyone is looking to catch out their neighbour.'
He said money and rank also played a role. 'There is a section of centres and prisons with individual rooms, colour televisions and air conditioning, and where you do not need to work. These rooms are available for money. You can also pay to have your sentence reduced. Among the police, work in prisons and detention centres has a low status, with less chance to make money than in other departments.'
The issue of who should run the detention centres was raised during the annual sessions of the NPC and CPPCC last month. Deputies, including legal scholars, called for the establishment of an independent body under the Ministry of Justice to take over their management from the Ministry of Public Security. Others called for officers of the procuratorate who work in the centres to have a greater role in supervising them.
'The lack of manpower means that the centres have to use inmates to control other inmates,' said Cheng Lei , a teacher at the law school of the People's University in Beijing. 'The lack of funds means that living conditions in them are rough. People are detained for a long time and have no contact with their family and friends or the chance to use the telephone. They are closed places, with a serious lack of effective supervision from the outside.
'Their problems are very complicated. They are both a place to detain people who have not been sentenced and also to interrogate suspects.'
Cheng proposed a new detention centre law, to take the centres away from the Ministry of Public Security and put them under an administrative unit of the Ministry of Justice; it would permit outside inspection by local representatives who could make unannounced visits and meet detainees, and inspect places where they were being interrogated.
He also proposed an independent medical system that would examine detainees when they enter and leave the centres and make independent evaluations of deaths.
These reforms are strongly resisted by the Ministry of Public Security, which argues that the centres are an important part of the crime prevention system, facilitating the work of the police in detaining and interrogating suspects. It argues that excessive stays, abuse and torture in the centres are separate issues, which should not be confused with the management of the centres.
Within the government, the ministry is a very powerful institution. The budget for internal security this year is 514 billion yuan, an increase of 9 per cent over last year, when it rose 16 per cent over 2008.
The ministry argues that norms and practices from developed countries are completely inappropriate for a country of the size, diversity and imbalanced economic development of China. For the past three years, the number of mass incidents of protest has exceeded 90,000, or an average of 247 a day. It argues that a unified and effective policing system is essential to prevent chaos.
These arguments have been broadly accepted by national leaders in the reform era - starting with Deng Xiaoping - who say that social stability is the priority and the pre-condition for economic development.
They point to Thailand as an example of how social conflict can damage a country.
So far the views of the ministry have been powerful enough to block any reform of the detention centres. In the future, they may again prove too powerful.