Hundreds of police officers gathered evidence from around the country for the trial of the mining tycoon Liu Han who is accused of running a mafia-style gang, state media reported.
Some 424 officers collected evidence from places as far-flung as Sichuan, Inner Mongolia, Shanghai, Macau and Hong Kong, the Hubei Daily reported yesterday.
Liu, his brother Liu Wei and 34 other accused members of his gang are standing trial in Xianning city, in Hubei province.
Liu Han faces 15 charges, including murder, financial crimes, running casinos and illegally selling firearms. He has denied the charges, according to more than three sources with direct knowledge of the matter.
The more severe charges against Liu include the murder of nine people over business disputes, the Hubei Daily said.
Liu's case is thought to be connected to the corruption investigation into the retired security tsar Zhou Yongkong.
A person with knowledge of the case previously said that the name of Zhou's eldest son, Zhou Bin has appeared in case files and transcripts of interviews with police.
Police interviewed more than 1,000 people in their investigation into Liu Han, according to the Hubei Daily. Liu, 48, was the former head of the mining company Sichuan Hanlong.
The court, which is posting updates of the proceedings on social media, said that three law enforcement officials in Liu's home province of Sichuan have been convicted of corruption and covering up the activities of gangs. Prosecutors said the three comprised a "political and legal umbrella" that had sheltered the Liu brothers' activities.
The convicted officials include Liu Xuejun, a former political commissar in the public security bureau in Deyang ; Lu Bin, another law enforcement official in the same agency; and Liu Zhongwei, a former deputy prosecutor in Shifang .
The court said the suspects helped Liu Wei find venues to run illegal casinos and provided him with firearms. In return, Liu Wei gave them cash, furs, luxury watches and cars.
The thirty-six defendants are standing trial in seven courts in Xianning. Defence lawyers have criticised the decision as unfair and illegal as defendants standing trial in one court would be unable to give evidence in another.
"The way of separating the trials and defendants does not have any legal grounds," defence lawyer Xuan Dong said.
The deputy mayor of Liu's home city of Guangyuan has been placed under investigation for corruption, according to Xinhua. Sun Liming, 46, is under investigation for "serious disciplinary violations".