Zhang says: "This miscarriage of justice not only damaged Zhang Gaoping and his nephew Zhang Hui, but also their families and even the public."
Zhang Biao who fought tirelessly to get two wrongful convictions overturned, is still striving to uphold the dignity of the law, Cao Yin reports.
Now that he has retired the focus of Zhang Biao's days should be looking after his grandson. But he says he seems to have spent most of his time giving speeches and doing interviews since last March, when£≠thanks to his efforts£≠two men walked free after spending almost a decade behind bars for a crime they did not commit.
In 2004, two truck drivers from Anhui province were found guilty of raping and killing a 17-year-old girl. Zhang Hui was given a death sentence and his uncle Zhang Gaoping was sentenced to life in prison by the Hangzhou Municipal Intermediate People's Court.
Their sentences were changed to a death sentence with a two-year reprieve for Zhang Gaoping and a 15-year prison for Zhang Hui at their appeal trial in Zhejiang Provincial Higher People's Court.
In July 2007, when he was a prosecutor in the city of Shihezi in the Xinjiang Uygur autonomous region, Zhang Biao was visiting the prison when he was told one of the prisoners would not admit his guilt and refused to accept correction.
"I didn't pay any attention at the beginning, because it is usual for some prisoners to be in such a mood during the early years of their sentences," the 63-year-old retired prosecutor says.
However, he soon found out that Zhang Gaoping was different.
"As I called him in the prison, he didn't reply 'here' like the others. Instead, he provided me with many written materials and said he had suffered wrongful treatment," the prosecutor says.
As a prosecutor with more than 30 years of experience, Zhang had addressed a few miscarriages of justice in his time, but he says that he had never before met a prisoner who had reflected on his treatment and the flaws in the case against him with such a strong desire and logic.
In June 2008, Zhang and his colleagues at the people's procuratorate in Shihezi held a special session to study the materials. They decided that there were grounds for Zhang Gaoping's claims of innocence and that he might have been tortured to extract a confession.
"Zhang Gaoping was in low spirits, but a little bit arrogant when I first talked with him. He didn't trust judicial workers, but thought the law could give him back his innocence," he says.
But the right to review and re-investigate the cross-regional case belonged to the prosecuting authority in Zhejiang, where the crime had taken place, instead of Xinjiang, where Zhang Gaoping was imprisoned.
Zhang Biao sent more than 10 sets of materials, including photos and documents, to the procuratorate in Zhejiang and even China's top court. Each of these sets comprised at least 100 pages. But each time he was told the evidence was insufficient to overturn the convictions.
Zhang Lu, his daughter, says the prosecutor was very down during this period, and she often heard him sighing in despair when he returned home.
But Zhang Biao's despair came to an end after he received a letter from Zhang Gaoping in August 2008, saying he had learned an inmate Yuan Lianfang had reported a man had made a confession in Henan province in 2002.
"I was shocked Zhang Gaoping's nephew had confessed to the murder of the girl to Yuan while they were detention together," he says. "I immediately contacted the prosecutors in Zhejiang and Henan, aiming to make clear why Yuan had provided similar testimony in different cases."
In July 2010, Zhang Biao confirmed the Yuan in the two provinces was the same man, and he had forced other detainees to plead guilty by beating them in detention houses so as to get his own sentence reduced.
To attract high-level judicial officials, Zhang wrote a letter to the chief procurator in Zhejiang, asking the authority to further investigate the case.
In 2011, Zhang Biao retired, but he still kept in touch with Zhang Gaoping's elder brother, asking him to get in touch with Zhu Mingyong, a lawyer who handled the case involving Yuan in Henan.
The case then became public after Zhu's assistant and a Shanghai-based reporter came to Xinjiang to get materials from Zhang Biao.
"I should thank the media, because the publicity forced the judicial bodies in Zhejiang to re-examine the case," the retired prosecutor says, adding he was also encouraged after the case was finally reversed.
"This miscarriage of justice not only damaged Zhang Gaoping and his nephew Zhang Hui, but also their families and even the public," he says. "Such mistakes can be avoided if every judicial worker pays more attention to their work and increases their sense of responsibility."
Although the wrongful convictions against Zhang Gaoping and his nephew have only been overturned about a year, Zhang Biao says he still receives almost 100 calls a day asking for his help.
"I'm retried and can't solve everything," he says with a sigh.
When he gives a speech, he suggests governments provide more specific procedures for judicial workers tackling appeals and should put such work on agenda.
"I also want the procedures to be issued as soon as possible, because my father's life has been affected by the case," his daughter says, adding she worries about her dad's health.