Hard as it is to believe that a prison guard could identify an inmate by just looking at the back of his or her head, that's exactly the prison guards in Guangdong's Sihui Prison are capable of. For this accomplishment, the guards have been hailed as the "most powerful brains" in the province's prison system.

Jie Haiye is one of the prison guards at Sihui Prison. He can use this method to identify up to 430 inmates. He said remembering each inmate's name and basic information is of fundamental importance to the prison's safety. It not only facilitates daily work but also helps the inmates feel respected so that they more willingly accept reform, according to Jie.

Zhu Hainian, a doctor in charge of over 100 inmates with mental disorders, has taught himself to discern who is a real patient and who is only pretending to be. Zhu said almost half of prisoners were jailed for murder.

Due to the coexistence of prisoners responsible for a wide variety of crimes, prison administration in Guangdong is becoming increasingly complicated, with penalties harder and harder to carry out. Medical parole cases are also on the rise.

Guangdong has been working toward a more transparent prison system since the end of 2014. In 2016, there were no incidents involving escaped convicts, nor were there any major safety accidents.

Guangdong prisons hold the largest number of criminals across the country.