Song Zhengguang wipes his tears with a glove after he was released on bail in Huaiyang county, Central China's Henan province, Jan 1, 2014. [Photo/CFP]

In April 2013, prosecutors withdrew the accusation, and Song was released on bail eight months later.

"At the end of 2014, Song's bail expired. So far there has been no explanation for the time my client spent in detention," Lin said, adding that a new judicial interpretation issued by the Supreme People's Court that took effect on Jan 1 provided some grounds for hope.