Chinese warehouse worker Liu Fei was fined 330,000 yuan ($54,200), or 14 times her yearly wage, for having a second child and her failure to pay means the boy has no access to basic rights like schooling and healthcare.
Liu's desperation prompted a fruitless attempt to sell her kidney and her 8-year-old boy's plea to sell his instead.
Their dilemma has now triggered a rare legal battle against the police for denying the boy a "hukou" - household registration - due to strict family planning laws.
The case will be heard in a Beijing court on Friday.
Liu's inability to pay the fine has left her son, Xiaojie, without an official identity. Family planning officials in Beijing told Liu in 2011 she would not be able to obtain a "hukou" if she did not pay up.
"When I saw (the fine), I thought this was inconceivable," a tearful Liu, 41, told Reuters. "I had no idea I would be fined so much. If I had known, I would never have given birth."
Liu's ordeal underscores the punitive nature of China's family planning policy, beyond the more well-known stories of forced abortions and sterilizations, and highlights the plight of an estimated 13 million undocumented children, known as "black children".
In China, "black" implies something illegal, outside of the mainstream or unofficial. Liu asked for her and her son to be identified by pseudonyms to avoid drawing attention.
Beijing gives local governments a wide mandate to enforce the one-child policy. Even as China relaxes the rules, allowing millions of families to have a second child, government encroachment into family matters will continue. Family planning officials will still require families to apply for licences to have children, leaving room for possible abuse.
Ma Jiantang, head of the National Bureau of Statistics, said in 2011 that in most of these cases, authorities denied children documentation because the families could not pay the family planning fines, media quoted him as saying.
In July, a 16-year-old girl in southwestern Sichuan was granted a "hukou" after she tried to kill herself by swallowing poison, media said.
"China is a country in which one is unable to move without documentation," said Yang Zhizhu, a former Beijing-based law professor, who lost his job in 2010 after he and his wife had a second daughter.
"Without a 'hukou', one cannot go to school, join the army, take an exam, get married, open a bank account or take a plane or train."
'You're like a puppy'
On Tuesday, a group of 10 lawyers and academics sent letters to four government agencies, including the State Council, China's cabinet, and the ministry of public security, urging them to review requirements to file for a "hukou" and scrap the need for fines to be paid first.
"Without this document, you're just like a puppy or a kitten, raised at home," said Huang Yizhi, Liu's lawyer.
"This is related to a person's most fundamental right, but because she didn't pay the social support fee, the police refused to give him (Xiaojie) a hukou. I think this condition is certainly unreasonable and illegal."
The fine, known as the "social support fee," is meant to go towards the government budget to compensate for resources and public services the child would use, according to state news agency Xinhua.
But there is mounting anger at the lack of transparency as to where the fees, which amounted to more than 16.5 billion yuan ($2.7 billion) in 2012, end up, according to Wu Youshui, a lawyer based in the eastern province of Zhejiang.
Wu said local officials had told him the fines were often either returned to village and township governments as rewards, or kept by county family planning commission officials "for their own expenses".
"The less developed the area, the more dependent the government is on birth-control fines, because they have very little tax revenue," he said. "Some village and township officials have told me explicitly: 'This is how we make money.'"
Liu's legal nightmare started in 2011 when she sought out the police and family planning officials to apply for a "hukou" for Xiaojie. According to family planning officials, Liu's son is considered her third child. She had been married and divorced twice - she has a 20-year-old daughter from her first marriage and her second husband also had a son.
Liu works in the warehouse department of an air-conditioning company, earning 2,000 yuan ($330) a month. Her two ex-husbands have died and she has tried to persuade officials that she should not be fined on account of her ex-husband's child.
Tried to sell kidney in desperation
On Friday, Liu goes to court. Police and local family planning officials could not be reached for comment.
Liu said she was so desperate at one point that she tried to sell a kidney. She looked on the Internet, but was told by some would-be buyers she was too old.
So Xiaojie came up with another idea.
"I went to the Family Planning Commission and said: 'My mother wants to sell her kidney'," he said in their apartment on the southern outskirts of Beijing. "I said: 'I wouldn't let my mother sell it, I'll sell my own kidney'."
Xiaojie attends a primary school close to his house which has not asked for his "hukou," though he will need it to register for high school and university.
Liu said she sought out a deputy director of the Family Planning Commission in the district of Fangshan, where she lives. He told her that her fine was the "lowest" possible.
Liu looked on the Internet for help and saw that a group of lawyers was demanding disclosure of the use of family planning fines. She got in touch with Huang, who took her case on for free.
But neither Huang nor Liu is hopeful.
"After all, the court and the police are all in the same area," Huang said. "Although there should be no relationship between an independent judiciary and the administration, in reality, there is a definite link, so it's difficult to say what the result will be. I'm not very optimistic."
The 2-year battle has taken its toll on Liu. She said she cried every day.
"If the law is fair, I think this problem will be solved," Liu said. "But who among us dares to believe in the law now? If this doesn't work, I will appeal. If I don't succeed, I will have destroyed my son's whole life."