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.