"The initial investigation conducted by Sonapur Police was allegedly neither impartial nor diligent. On the contrary, serious attempts were reportedly made to destroy crucial evidence, including the burning of the victim's house after the incident," it said.

It further said that a prime accused, Arjun Bordoloi, was killed under mysterious circumstances on September 5, 2012, raising further concerns regarding the integrity of the investigation.

Subsequently, the case was transferred to the Criminal Investigation Department (CID) and on December 7, 2017, two police officers -- Pranab Kumar Deka, the then officer-in-charge of Sonapur police station, and A M Choudhury, the then investigating officer of the case -- were arrested on charges of deliberately destroying evidence with the intention of shielding the actual perpetrators.

The case was handed over to the CBI a year later by the state government.

Despite sustained protests and representations submitted by numerous local ethnic and social organisations over the years, the authorities concerned have remained largely unresponsive, the Manch alleged.

"...it is humbly prayed that your esteemed office may kindly take cognisance of the grave human rights violations involved in this case and intervene appropriately to ensure a fair, independent, and time-bound process leading to justice for the victims," the petition said.

All responsible for the crime as well as for the obstruction of justice be brought to book in accordance with the law, it added.