Once there, he would inject her with an orange liquid or feed her a cold drink likely laced with drugs to immobilize her, then tie a belt around her neck and rape her, she later told her older sister. He invited the complex’s security guards, plumbers and electricians to join.

Over the course of seven months, they, too, raped and molested her, possibly dozens of times, using makeup to cover any marks they left on her, her sister said.

© Andrew Caballero-Reynolds/Agence France-Presse — Getty Images A rally in 2012 after the cremation of Jyoti Singh Pandey, who was raped and beaten by a group of men and later died from her injuries. The brutal crime prompted wide-ranging changes around the discussion of sexual assault in India.

A current of rage shot through Chennai last week after the police arrested 17 men, ages 23 to 66, for the assaults. Lawyers beat several of the men as they were curled up on the floor of a local courthouse.

Frantic residents of the building where the girl lived organized round-the-clock shifts guarding the entrance.

But a few days later, the police stopped answering calls from reporters. Around Chennai, people blamed the mother. They erroneously said the girl, who wears hearing aids and acted younger than her age, was “deaf and dumb.” They dismissed questions about women’s safety.

The girl’s older sister, whose name cannot be revealed by Indian law, said she was furious at the turn of events. As with other violent assaults against women and girls that have shaken India this year, the victim was getting the blame, shifting the focus from the men’s behavior, she said.

“If we shy away from conversations about sexual assault, the only thing we are conveying to young boys and girls is that the issue is not discussable,” the sister said. She referred angrily to a news report about a woman who said she was raped by 40 men over four days.

“That’s how men grow up in the society. They are taught to dominate women.”

Discussions about sexual assault are changing in parts of India, where harassment has long been dismissed indulgently as “eve teasing.” The transition accelerated in 2012, when a 23-year-old woman riding a private bus in Delhi was attacked by several young men, violated with an iron rod and left on the side of the road.

Two weeks later, the woman, Jyoti Singh Pandey, died from her injuries and protesters flooded streets all over the country. The government created a fast-track court for rape cases and introduced capital punishment for especially brutal sexual crimes.

But some of the country’s most vocal women’s rights advocates warned that passing tougher laws would not magically prevent crimes against India’s girls and women.

© P. Ravikumar/Reuters A police vehicle carrying men accused of raping an 11-year-old girl came under attack this month in Chennai, India.

A study released this year found that more than 99 percent of sexual assaults in India are never reported. And in those that are, police investigators intimidate women into changing their statements or use invasive “two-finger” tests to determine whether they had a prior sexual history.

If the answer is yes, the conviction rate plummets. Even if a case makes it to court, women sometimes wait decades for justice.

“The problem is not the law or the severity of the punishment,” said Shruti Kapoor, an Indian economist and women’s rights activist. “The problem is the broken judicial, political and administrative system. What use is a law if it’s not implemented properly, if the system is plagued with corruption and it takes years for victims to get justice?”

Rajat Mitra, a psychologist with decades of experience interviewing convicted rapists and working with Indian officials, said that in parts of the country, it was still common for people to see rape “as less of a crime and more of a social deviation or aberration against the family honor.” Girls and women are often blamed, he said. Politics sometimes creeps in.

This year, Hindu lawyers blocked police officers from charging a group of Hindu men accused of raping and killing an 8-year-old Muslim girl in northern India. They said the men had been set up and were innocent.

In May, a teenage girl who was gang raped in eastern India was set on fire by one of her attackers after her parents reported the crime to a village council.

It is hard to track the rise or fall of sex crimes anywhere in the world, partly because so many are not reported. But in India, Mr. Mitra, the psychologist, said that the prevalence of gang rapes has risen as fissures over issues like caste are pushed into public view and men migrate to cities from rural communities, where regressive attitudes toward women are common.

“There are a greater number of groups of men roaming the Indian streets who carry an aura of anonymity and are not rooted in the city,” he said.

© Arun Sankar/Agence France-Presse — Getty Images A demonstration in Chennai in April over the rape and murder of an 8-year-old girl in northern India. The case quickly became defined by tensions between Hindus and Muslims.

After the initial news of the Chennai assault, Kavya Menon, the secretary of Aware India, a group that organizes local workshops about child sexual abuse, said her phone had been ringing constantly. Most callers were mothers worried about their daughters.

Ms. Menon said she saw such responses after almost all of India’s widely reported rape cases. But then the initial outrage would subside, she said, and people would fall back into denial about the prevalence of sexual assault or rationalize the crime.

“Shame is so strong,” she said. “And people really don’t understand that the shame has to be with the perpetrator.”

Around Chennai, public conversations about the 11-year-old girl’s assault changed shortly after the men were arrested.

A female police constable said that only one or two cases of sexual harassment were registered every year in the city, one of India’s largest and home to millions of people. A representative from Tulir, one of the few local organizations working to curb child sexual abuse, declined to speak about child sexual abuse or the case of the 11-year-old girl, saying the men had not been convicted.

Asked about the prevalence of sexual crimes in Chennai, a senior police official, M. C. Sarangan, said he wouldn’t know.

“Her parents did not care about her,” Sasikala, 30, a seamstress who goes by one name, said of the girl.

The girl’s sister said it was hard to say whether any of the residents had seen anything suspicious. The men were familiar faces hired to guard and service the building of several hundred units.

This month, the sister pulled the pieces together while visiting Chennai during a college break. As the sisters rode the elevator one day, the attendant touched the 11-year-old’s arm suggestively and she did not pull away.

“I asked her, ‘Why didn’t you say anything to him?’” the sister recalled. “I kept asking her again and again, and then finally she opened up. My mother broke down. My dad did not eat anything for two days.”

The family rushed to the police. Neighbors offered food and legal advice. The authorities found that many CCTV cameras were not working inside the complex, she said.

At least three of the men confessed to raping the girl, the sister said the police told her. Hospital tests confirmed that she had been assaulted, a police officer said separately, and paraphernalia used to drug the girl was also recovered.

But in the days after the men were arrested, the sister said attacks against her family became sharper and the focus on the men’s roles receded.

“She was blackmailed by these men, saying that they will murder her mother,” the sister said. “The frightened daughter would not open up to her mother. Justice is a very significant part of the matter here and people want to hold the parents responsible.”