"That conversation ended my son's life," his mother, Rekah, told Fairfax Media this week.

The last time Nitin's parents saw their 17-year-old son alive was on Monday, April 28.

"He woke up early, did his routine, and left for school without breakfast. It's five minutes' walk from here," says Rekah. "The last thing he told me was 'I will be home for lunch'."

Home is a tin shed with a dirt floor near a crossroads on the outskirts of Kharda, a remote village 330 kilometres east of Mumbai in the state of Maharashtra.

The Aage family have squatted there on state-owned "encroached land" for the past 12 years.

They have enough electricity to power a single light bulb, but no other facilities, such as running water, or a toilet. Cooking is done over a wood fire.

"I moved here because it is close to a good school," says Nitin's father, Raju. "We migrated here from my native district about 80 kilometres away."

The Aage family are "untouchables", or Dalits, a Marathi word that means "broken people", who are excluded from the Hindu caste system and sit at the bottom of India's rigid social hierarchy. They number a quarter of the country's 1.2 billion people.

Before his son was murdered, Raju, who is 55, worked in a nearby quarry crushing rocks for 150 rupees a day, about $2.80, while Rekah, 50, stayed home to look after their four children. Nitin was their only son.

"He was a quiet boy, focused on his education and a career," says Raju. "My dream was for him to join the army as an officer. As a backup, I wanted him to become a mechanic."

To learn how engines worked, Raju encouraged Nitin to spend his spare time working without pay at different motor repair shops in Kharda.

"If he wasn't at school, he would be working at one of the garages," says Raju. "He was good, especially at repairing motorcycles. People would ask for him."

When Nitin came home from school on that critical Saturday, Rekah sensed his fear.

"He wanted me to come to the school on Monday and tell the girl that he would not buy her a phone, and not to talk to him again."

The girl was Pooja Golekar, 17, who was born into the powerful Maratha sub-caste.

The Marathas are part of the Kshatriya warrior caste and claim to be descendants of Shivaji, the 17th-century Hindu leader who overthrew Maharastra's Muslim rulers in 1659.

Today, Marathas dominate the state, holding most of the land and much of its political power. In recent parliamentary elections, Marathas won 146 out of 288 seats in the state's lower house.

When Monday came, Rekah followed her son's instructions and went to the school, some time after 11am, but she missed Pooja. It was the last day of term and school had already broken up for the summer.

Raju, who was working at the quarry that day, recalls that about 11.30am the son of the quarry owner came to him and said there was trouble involving Pappu, Nitin's nickname.

"He told me the names of the boys who attacked Pappu. They were the names of his friends. He was with them every day, so I did not believe it."

Concerned nevertheless, Raju left the quarry and walked into Kharda to a garage where Nitin worked. Unable to find him, he persuaded someone to call one of the boys who was supposedly involved in the attack.

"We kept ringing. Eventually he picked up. He informed us that it was true. Nitin had been severely beaten and he was somewhere on the outskirts of the village."

By this time, Rekah was also worried.

When she had returned home from the school, her daughter told her a boy named Akash Survey, whom she knew to be a friend of Nitin's, had stopped by the house on a motorcycle and shouted out: "We beat up Pappu very badly."

Suspecting it had something to do with Pooja Golekar, Rekah went to the Golekar family home.

"They told me, yes, they had beaten up my son, but then they told me that he would come home soon and to go away and wait for him."

Rekah began searching for her son in the hilly scrubland surrounding her home that is used mainly for cattle grazing.

At the same time, her husband was piecing together the story of what had happened to Nitin from people in Kharda.

Nitin, Raju learnt, was first beaten at school. The ringleader, Raju was told, was Pooja Golekar's 25-year-old older brother, Sachin. Nitin's friend, Akash Survery, 17, was also involved.

Nitin tried to get away, going to one of the garages at which he worked, but they followed him, dragging him out the back of the workshop to beat him again.

The gang, who by this time numbered about 13, then drove Nitin to a water reservoir in a gully off the main road in the scrubland behind the Aage family home.

"It was around 3pm by this time, I was still in Kharda, and then it was my own brother who came to me and said Nitin was no more," says Raju.

Raju was led to a place overlooking the water reservoir, where he found Nitin hanging from a tree. A rope had been tied around his neck.

In photographs taken at the scene, Nitin's white long-sleeve shirt is torn down the middle. His face is swollen and bruised. A medical examiner later concluded Nitin had died of asphyxiation.

"They killed my son because of caste," says Raju, unable to contain his anger and grief as he walks back to the place where his son died. "My only son, taken from me, because we are Dalits."

Sachin Golekar, Akash Survey and four other men have since been remanded in custody awaiting trial for murder. Seven other men who are facing lesser charges related to Nitin's death have been released on bail.

In the uproar that shook the state of Maharashtra after Nitin Aage's death, the Golekar family have made no attempt to hide their involvement, or the motive.

Nitin, they maintain, was having an affair with Pooja. Why else would she ask him for a phone, they reason, than to stay in touch with him over the summer holidays?

Whenever Raju sees the accused in court, or passes their relatives in the street in Kharda, they revel in reminding him of what happened by slowly twisting the ends of their moustaches with a thumb and forefinger.

"It's difficult to overstate the impact of this atrocity on the family," says Dr Nitish Nawsagaray, an assistant professor of law at ILS Law College in Pune. "Not only was he the only son, he was the first generation in this family to be educated. He had a passport to a better life, for him and for his family."

Fairfax Media was unable to interview the families of the accused, but Ashwini Satav, a crime reporter for the Pune-based Marathi newspaper, Punyanagri, did manage speak to the Golekar family after Nitin's murder, and she confirmed the family was proud of what had happened.

"They believe they have defended the honour of their family and their caste, and that justice was done," says Satav.

As for Pooja Golekar, adds Satav, she also is a victim.

"She has not been allowed to leave the house or attend school. Her family are trying to arrange a marriage with someone in another district. 'Who is this Nitin Aage', she said to me, 'I didn't even know him'."

Priyadarshini Telang, the convener of the Maharashtra branch of Dalit Adivasi Adnikar Andolan, a national movement founded last year to improve the lives of Dalit and Adivasi tribal communities, says there have been 12 caste murders in Maharashtra this year.

"Those are the murders we know about. Sometimes the power of the dominant caste is such that the crime is not reported," says Telang.

According to India's National Crime Records Bureau, a crime is committed against a Dalit by a higher-caste Hindu every 16 minutes. Every day about four Dalit women are raped by higher-caste men. Every week about 13 Dalits are murdered.

"That's just the rape and butchery," wrote the Booker-prize winning author Arundhati Roy in an essay published earlier this year that boils with rage at India's institutionalised system of social stratification. "Not the stripping and parading naked, the forced shit-eating [literally], the seizing of land, the social boycotts, the restriction of access to drinking water."

The essay forms the introduction to a new edition of Annihilation of Caste, a scathing demolition of Hindu customs published in 1936 by Dr B. R. Ambedkar, the brilliant founder of India's civil rights movement who broke free of his "untouchable" upbringing to help author India's constitution.

Roy's use of the word butchery is neither careless nor exaggerated.

When Priyadarshini Telang, the Dalit activist, spoke to Fairfax Media in Pune on Tuesday, it was after he had attended a meeting on how to move a stalled investigation into the murder of a Dalit family of three on October 20 in a district near Kharda.

"The people they are consulting to rewrite the school curriculums are not secular groups, but very ideological, religious Hindu groups. That will only strengthen the caste system."

Telang opened the photographs of the victims stored on his laptop. They showed the mother, Jayshree Jadhav, aged 40, who had been beaten to death. Her husband, Sanjay, 42, had been cut in half at the waist. Their 19-year-old son Sunil's arms, legs and head had been severed from his torso.

Police found Sunil's arms and torso in a well near his home two days after the family was reported missing, along with the bodies of his mother and father.

They found his head, which had been split in two, and both his legs, stuffed into a narrow bore well the following day.

"No one has been arrested in this case, and the motive is not clear, but the violence directed at Sunil suggests he was the main target. Due to his age, we think a love affair is involved," says Telang.

Sunil himself had announced he was in love, on his Facebook page, where he had also posted an unidentified photograph of a beautiful, dark-haired woman aged about 18.

In the photograph, which was taken in a corn field, the woman is kneeling side on to the camera with a hand tucked under her chin. She is wearing a printed white tunic and is looking into the camera with a Mona Lisa smile.

"When a Dalit crosses the line of love and status in our caste society, what they get is a brutal death," says Telang.

Despite an act of law that requires all state governments to try caste-atrocity cases in special courts, Telang says no such court has ever been established in Maharashtra.

The state is also required to quickly appoint a special public prosecutor to such cases to enhance the investigation, but authorities are yet to name a special prosecutor over the deaths of Nitin Aage or the Jadhav family.

The biggest obstacle preventing change, argues Telang, is that governments of all persuasion in India, be they Congress or the ruling Hindu nationalist Bharatiya Janata Party, are embarrassed by caste atrocities and do everything they can to pretend they are not happening.

"The Congress Party preaches a secular message, but their participation within the caste system gives them little reason to change it. For the 60 years they have governed India, the Congress has always put caste first. The Congress is a green snake in the green grass."

At least you know what the BJP really stands for, says Telang. They are like a white snake in the green grass.

With Narendra Modi about to become the first Indian prime minister to visit Australia in 28 years, Telang says his major concern about Modi's first few months in government are his plans to focus India's education system even more on reinforcing Hindu values.

In Nitin Aage's case, Telang explains, a special prosecutor probably will be appointed when the case comes to trial, but that will be too late to have a role in collecting evidence and strengthening the case.

"There are only one or two Dalit witnesses. Everyone else is from the higher caste. There will be enormous community pressure on the witnesses at the trial. The facts of the case are clear, but the chances of a conviction are low."

Jitendra Shiktode, a 23-year-old university student from a Dalit family in Ahmednagar in Maharashtra, told Fairfax Media it was Mohandas Gandhi, a staunch defender of the caste system, who most famously romanticised village life in India.

"What most people do not know is that the Indian village is a deadly place."