Tarannum Cheema moved to Delhi from Chandigarh in 2009 to assist her father RS Cheema.

Highlights RS Cheema was the CBI's special prosecutor in the case

His daughter, Tarannum, was assisting him

Sajjan Kumar convicted to life in prison in anti-Sikh riots case

The Delhi High Court verdict that overturned the trial court's acquittal of Sajjan Kumar in the 1984 anti-Sikh riots case was a rare moment of success for the Central Bureau of Investigation.

Around 3,000 Sikhs had died as armed mobs unleashed violence in Delhi after then prime minister Indira Gandhi was assassinated by her Sikh bodyguards on the morning of October 31, 1984. Eyewitnesses said the mobs were led by Congress leaders - Sajjan Kumar was the first senior leader of the party to be convicted.

While the victims' lawyer HS Phoolka is a well-known figure, the agency also had an all-Sikh prosecution team that involved a father and daughter.

RS Cheema was the special prosecutor whom the CBI team approached to take over the case in 2010.

Mr Cheema, known for obtaining many convictions for the agency in the coal scam, including that of high-profile IAS officer and former coal secretary HC Gupta, had to commute between Delhi and Chandigarh to handle the '84 riots case. His daughter, Tarannum Cheema, had recently got her law degree and was assisting her father as his junior.

"I would actually give her credit for the work," Mr Cheema told NDTV on phone from Chandigarh. "She moved to Delhi to handle the case. She had to handle all the witnesses".

Sajjan Kumar was found guilty in the 1984 anti-Sikh riots.

The conviction of Sajjan Kumar, who reportedly wrote to Congress chief Rahul Gandhi that he is quitting the party after the verdict, is based on the testimony of two women - Jagdish Kaur and Nirpreet Kaur - both of whom lost family members in the riots that hit their colony at the Delhi Cantonment.

Ms Cheema had to move as someone had to sit through the trial to ensure that the women would not be intimidated by the drawn-out cross-questioning process.

At one point, Nirpreet Kaur realised that the case didn't relate directly to the murder of her father, Nirmal Kaur. And so it took persuasion to ensure that she continued to testify, despite it not being directly related to her own loss.

Nirpreet Kaur had to leave her home in Amritsar and stay at Punjab Bhawan for two months during her cross questioning.

"They would keep trying to underestimate them, they called them liars, they even called Nirpreet a terrorist because she was jailed as a student leader," said Tarannum Cheema, clarifying that all cases against Nirpreet Kaur were later dropped. "We had to reassure her that there was no need to feel like they were on the backfoot, they just had to stick to the truth."

While the CBI gathered evidence and witnesses, what really helped was the police daily diary of Raj Nagar that the Cheemas presented in court. The police log recorded the Delhi police as noting the week of the riots between November 1 and 11 as nothing significant happening even though 341 people had been killed in that one police post. This shocking silence of the police report made the High Court judges note the police attitude towards the "atrocities".

35-year-old Tarannum Cheema is not done yet though. She is now the Special Public Prosecutor in her own right, fighting Sajjan Kumar in the second riots case relating to Sultanpuri.

Did the fact that she and her father are Sikhs motivate her more? "My father is born in 1947, so he is a child of partition. We will fight against any communalism, not just those directed against Sikhs,'' she said.