As Bo Xilai stood in court to receive his life sentence last month, there could be no mistaking the faint smile of the Chinese politician who seemingly fell victim to his own political success.

But despite the unusually public nature of his demise, many in China were unconvinced that the man appearing in court would serve the punishment. Throughout the trial, posts on social media demanded to see pictures of Bo in his cell to prove that he was really there.

The online claims levelled against his wife, Gu Kailai, hinted at an even greater level of deception – that she was not in the courtroom at all. Images comparing her previously slim face with photographs of the plump-cheeked woman on trial were widely circulated on the net.

These allegations may seem far-fetched, but they are based on what many perceive to be a growing phenomenon. Media reports of ding zui (literally “substitute criminal”), where hired stand-ins take the place of offenders, suggest that such immunity to the legal process can be acquired with sufficient money or influence.

The use of this practice is, by its very nature, difficult to gauge. Very few high-profile figures have been implicated, but a 2009 case involving an official in Anhui province showed the influence that the powerful can exert to redirect blame.

Reversing his car at high speed, the former head of Yijiang’s district court, Ding Shuming, killed one person and injured two others in a road accident. He arranged for his usual driver, Zhong Ming, to report the incident to the police and take responsibility for the accident. Zhong agreed, though a late act of conscience from Ding two days later ensured that the right man appeared in court. He received a three-year jail sentence as a result.

It’s unclear whether hierarchical allegiance or financial gain motivated the driver’s willingness to take responsibility. However, other attempts at ding zui give an indication of the sums of money that may be involved.

An uninsured coach driver in Gansu province, whose name was reported only as Mr Li, killed one person and injured another after he crashed into the back of a motorcycle in July 2012. As he awaited the police, Li pleaded with one of the coach’s passengers to take his place and go to court, offering 150,000 RMB (£15,400) in return.

As the evidence was prepared for the hearing, inconsistencies emerged. Only after several rounds of questioning did the passenger eventually confess to the scam leaving Li to face trial, though his sentence was just one year and two months imprisonment.

Such attempts at ding zui are publicly reported by China’s domestic media, despite the notoriously opaque legal system. But it is impossible to ascertain how many instances are discovered at a stage that would imply official failures and thus dissuade courts from releasing the information. But an openly reported case in neighbouring Taiwan demonstrates the drastic extent to which the practice could be exploited in mainland China. Guo Ronghui, a 25-year-old a destitute drug addict, managed to forge a career as a professional body double.

Because he had been diagnosed with leukaemia, Guo was eligible for “medical parole”, exempting him from serving time for minor offences. He exploited this loophole to lucrative effect. It is alleged that he acquired 172 separate criminal records as a stand-in. He was sentenced numerous times, mainly on others’ drug and firearms charges, and accumulated prison sentences amounting to more than 48 years. None were served.

Guo typically charged his clients the equivalent of £5,000 to £10,000 per case and although many simply fled after paying their deposits, it is estimated that he earnt more than £60,000 as a scapegoat as well as accepting drugs as payment. In 2007, when questioned for violating the terms of his parole, Guo admitted to police he had been acting as a criminal body double for a decade.

Such examples highlight the dire financial and personal circumstances that push stand-ins into become willing scapegoats. The amount offered can vary hugely. In mainland China a demolition company owner charged with illegally destroying a house promised an impoverished body double approximately £20 a day for each day spent in jail on his behalf.

On the surface this phenomenon appears symptomatic of growing income inequality in modern China, but the explanation may be more deeply rooted, according to Geoffrey Sant, a lawyer and professor at Fordham Law School in New York.

His research on ding zui, due to be published next year, finds examples of body doubles being hired for imprisonment, physical punishment and even execution dating back to the mid-1600s. As well as financial gain, he attributes the continuation of the practice to cultural and family pressures. “The typical examples... are where somebody either surrenders themselves for their family member because they can get a lesser punishment, or because that person is the breadwinner and taking their place means the family still has income.

“It seems like this may be the dark side of filial piety, the Confucian ideal of sacrificing yourself for your parents,” he says.

The pressure of loyalty in a hierarchical society and the promise of sizeable payoffs provide somewhat diverse motivations for substitute criminals. But it is failings in the Chinese criminal justice system that may be encouraging the phenomenon to flourish, says associate law professor at the Chinese University of Hong Kong, Eva Pils.

“You have a system that is in effect tolerant of false confessions,” she says. “The trial should be held to determine whether the defendant is guilty or not but ... it becomes a merely bureaucratic process, a procedure to go through.”

Given that the acquittal rate in Chinese courts is less than 1 per cent, if a substitute criminal makes it to the stand, then the chance of exposing ding zui falls drastically. The lack of judicial transparency, infrequent use of witnesses and officials turning a blind eye to the practice make it a viable option for the accused.

“Pressure put on police and prosecutors to solve crimes can be very direct because their performance assessments require them to close cases, and there is a well-known practice of pressurising investigators to ‘crack’ the case within a stipulated time-frame,” Pils says.