The sadistic crime sparked international outrage and renewed attention on India's rape culture. The case even prompted the country's parliament to strengthen rape laws by setting tougher penalties, such as adding the death penalty as a possible punishment.
Only, as next week marks seven years since the crime, the story still isn't over.
First, in March 2013, the bus driver and gang leader Ram Singh was found dead in his prison cell. Indian authorities admitted there was a "major security lapse" behind how Singh's cell mates and prison guards didn't prevent the alleged suicide.
In September of that year, an Indian court found Thakur and the three other remaining men guilty and sentenced them to the death penalty. The sixth assailant was released because he was a minor at the time of the crime.
The defendants appealed. In 2017, India's Supreme Court rejected a plea to review the death sentence due to the four's "brutal, barbaric and diabolical" conduct.
All the while, pressure remained on Indian authorities to deliver on their pledges to stop violence against women, even as gruesome rapes of women there continue to make international headlines.
Then Thakur's lawyers began presenting a new argument.
India has some of the world's most toxic air. And it's the worst in New Delhi, which the World Health Organization has labeled the globe's most polluted major metropolis. Delhi state's chief minister, Arvind Kejriwal, has repeatedly called the region a "gas chamber."
Thakur's lawyers cited Kejriwal's statement as they argued this week that the death sentence should be commuted because of Delhi's pollution and water "full of poison."
"Life is going short to short, then why the death penalty?" the petition read, CNN reported.
Legal experts dismissed the argument as a stalling tactic and said it wouldn't work.
Still, Thakur's lawyer isn't backing down.
"He's a poor man," he told CNN. "His parents are old and helpless. Pollution is anyway harming lives and killing people slowly. Give him a life term sentence, not the death penalty."
The shocking way convicted rapists justify their crimes
There are many opponents of the death penalty around the world who cite different reasons for opposing the practice: The act violates religious beliefs and, some argue, is cruel and amounts to torture. In the United States, advocates point to how the practice has historically discriminated against African Americans and other racial minorities, and has also ensnared those with mental illnesses and wrongful convictions.
In this week's petition, Thakur's lawyers did not cite another case in which the argument has worked.
But in other countries and communities, such as Iraq and Malaysia, judges will dismiss rape cases if the perpetrator marries the victim, who is often treated as an outcast after such assaults. Many legal codes in Asia, Africa and the Middle East don't recognize rape within a marriage as a crime. In Spain, men have been acquitted of rape when their victim has been unconscious because of a highly controversial requirement in the law that the assault has to be forced - and an unconscious victim, the justification goes, can't fight back.
Before his death, Singh, the bus driver, made another argument against the death penalty and his rape charge in a documentary screened on the BBC.
The woman, Singh first argued, was responsible for her own assault.
"A decent girl won't roam around at nine o'clock at night," he told the filmmaker, Leslee Udwin. "A girl is far more responsible for rape than a boy. Housework and housekeeping is for girls, not roaming in discos and bars at night doing wrong things, wearing wrong clothes."
He then went on to argue that she shouldn't have fought back - and that the death penalty only made men more likely to kill their victims rather than leave them alive.
"When being raped, she shouldn't fight back," he said. "She should just be silent and allow the rape. Then they'd have dropped her off after 'doing her' and only hit the boy . . . The death penalty will make things even more dangerous for girls. Now when they rape, they won't leave the girl like we did. They will kill her. Before, they would rape and say, 'Leave her, she won't tell anyone.' Now when they rape, especially the criminal types, they will just kill the girl. Death."
Indian researcher Madhumita Pandey interviewed hundreds of Indian men convicted of rape as part of her doctoral thesis to try to better understand the roots of rape culture and toxic masculinity.
One of her main conclusions indicted all levels of society. "In my experience a lot of these men don't realize that what they've done is rape," she said. "They don't understand what consent is."
She continued, "There were only three or four who said, 'We are repenting.' Others had found a way to put their actions into some justification, neutralize, or blame action onto the victim."
