Police officers in Kunming, Yunnan Province arrest two people who organized prostitution in a residential community in February 2015. Photo: CFP

The mysterious death of a young father who was detained during a raid on a foot massage parlor in Beijing has triggered public outcry, raising suspicions of police brutality and abuse of official power, with many demanding an impartial investigation into the case.

Though they have assured the public that 29-year-old Beijinger Lei Yang was detained for legitimate reasons, Beijing's Changping district public security bureau has so far failed to prove they did not cause Lei's death through excessive use of force.

Since Lei died while in police custody in Changping on May 7, the police have only said that Lei died of a heart attack and that he was arrested while soliciting a sex worker. They failed to provide any further details regarding the exact circumstances of Lei's death or any evidence supporting their claims.

"Local police should steer clear of public suspicion and let the procuratorate release the results of the investigation, as internal investigations by the police are not seen as convincing," Mo Shaoping, a law professor at the Central University of Finance and Economics, told the Global Times.

Responding to the public outcry, the People's Procuratorate of Beijing's Changping district has stepped into the investigation, though further details haven't yet been revealed, the Xinhua News Agency reported on Friday.

Law enforcement supervisor

"Theoretically, the procuratorial organ's intervention in the case has two main purposes. It is to supervise police's law enforcement actions to determine if their actions were legal, and to investigate the police's dereliction of duty," Mo said.

"Though the details of the procuratorate's investigation are unclear, it's very likely that the investigation will equally focus on both purposes, as the public is furious about the police's possible abuse of power and are demanding an impartial result," Wang Sixin, law professor at the Communication University of China, told the Global Times.

According to the Criminal Procedure Law, crimes involving official dereliction of duty or violations of a citizen's personal rights by State functionaries should be placed on file for investigation by procuratorates.

"Due to the complexity of the case, the procuratorate will have to collect enough evidence to determine if it will file a case against the police or not," Wang said.

Lei's wife filed the case with the People's Procuratorate of Beijing Municipality on Tuesday and the procuratorate is expected to decide whether they will accept the case within the week, Chen Youxi, the lawyer representing Lei's family, told the Global Times on Tuesday.

"Normally, the case should be under the investigation of the People's Procuratorate of Beijing's Changping district. But Lei's case is quite sensational and should be investigated by a procuratorate at a higher level to ensure the impartiality and credibility of the investigation," Mo said.

Lack of power

Though the law stipulates that procuratorates and public security organs should divide their responsibilities and check on each other to ensure the correct and effective enforcement of the law, the latter group has much more power and is rarely supervised by procuratorates effectively in practice, experts said.

"Currently, China's public security organs, especially police stations at the local level, have been given great trust in law enforcement, while corresponding supervision institutes', especially procuratorates, supervisory functions are diminished. Only when a big case like Lei's happens, will they intervene in police investigations," Wang said.

"Due to their lack of necessary resources and technologies, the procuratorates usually need the police to assist them [when they are investigating the police], making the results less impartial," Mo said.

"The country should give more rights to third parties, such as the media, legal experts and the people involved in the case, so that they can also participate in supervision of the public security organs," Wang said.