A Special CBI Court on Tuesday started the trial in the sensational Sheena Bora murder case by framing charges against her mother Indrani Mukerjea, and her two step-fathers - former media tycoon Peter Mukerjea and Kolkata-based businessman Sanjeev Khanna.

The trio has been charged with the murder, kidnapping, abetment to murder, hatching a conspiracy and other charges, of the 24-year-old Sheena, a former executive with Mumbai Metro One Pvt Ltd, on April 24, 2012.

The accused trio pleaded "not guilty" to the charges, and the matter was posted for next hearing on February 1 when the trial will start.

Special Public Prosecutor in the case, eminent criminal lawyer Ujjwal Nikam, said the minimum punishment in this case is life imprisonment and the next procedure for the prosecution would be to prove its charges against the accused.

Indrani and her ex-husband Khanna were arrested in August 2015 along with her former driver Shyamvar Rai, while Indrani's present husband Peter Mukerjea was nabbed in November that year.

The Mukerjea couple and Khanna have remained in police and CBI custody since their arrests.

In June 2016, Rai turned an approver in the case in return for a pardon by the CBI Special Court.

Later, he was understood to have provided valuable information pertaining to the grisly killing of Sheena to the CBI, which took over the probe from Mumbai Police in end-2015.