NEW DELHI: September 30, 2008, 3.45am.

Cops had rushed to a call of an apparent accident of a Zen car DL 2CR 5801 on Nelson Mandela Marg in south Delhi.When they reached the spot, they found a woman in the driver's seat in an unconscious state.

Blood was oozing from her head, which was titled to the left.

A phone was ringing in the car.

The police took the call and spoke to the woman's father on the other side.This is how the Soumya Vishwanathan was found.After an autopsy confirmed a bullet in her head, police started a homicide investigation.Special commissioner HGS Dhaliwal, then the DCP of south district, told TOI on Sunday that the use of a country- made firearm and the absence of any apparent motive or a witness or CCTV footage made the case a huge challenge for the police at that time."We never lost hope.

The progress in the case was reviewed every day till the perpetrators were caught.

The family was also part of these meetings and they were updated regularly," Dhaliwal said a day after a city court awarded life sentence to the four killers - Ravi Kapoor, Amit Shukla, Baljeet Malik and Ajay Kumar.

Dhaliwal always stayed in touch with the family during the probe and offered all assistance.Recalling the extensive investigation at the time, Dhaliwal said one of their initial strategies was to use "traffic forensics" in the case.

"Flow dynamics with simulation was carried out with the help of a private traffic forensics lab.

Sequencing of probable events in the given circumstances was done by the experts.

The entire route was retraced from the office of victim to the place of the incident," he added.It was a PCR van that alerted the police about a WagonR with four persons having come to the spot and enquired just after the incident.

So, efforts were made to simulate the route of the WagonR to identify their occupants.

"Analysis of call details of 122 contacts of the deceased was done.

85 persons were examined based on the dump data analysis and 4-5 persons found to be on spot in the given window of time were questioned at length," the investigator said.Ballistics and forensics comprised a major chunk of the investigation.

"Efforts were made to find out the trajectory of the bullet fired at the victim, the direction of firing, height from which the gunshot came, the distance from which the shot was fired," Dhaliwal said.The forensics team inspected the victim's vehicle to ascertain the speed at the time of incident, whether a tyre burst was due to collision with a divider and if there was a possibility of collision with another vehicle moving in the same direction."Later on, the accused's vehicle was inspected to match the corresponding impact/damage to the car and to prove that corresponding dents were repainted," he added.In total, 24 teams - comprising then ACP Bhisham Singh, inspectors Atul Kumar Verma, Jai Prakash, OP Thakur and others - worked round the clock for months but a breakthrough didn't come.

Although, no major crime was reported in the next six months, a similar murder was reported in March 2009 when an IT executive named Jigisha Ghosh was shot dead in her car in a similar manner on the same stretch.In that probe, CCTV footage of one accused, while he was using robbed credit card of the deceased, came to the police.

This was developed in high resolution.

The suspect, Ravi Kapoor, was identified by a beat constable.

He turned out to be a police informer.

Having knowledge about the probe developments, he had been able to shield himself and his aides while taking the cops on a wild goose chase several times.The accused was tracked down and arrested on March 24, 2009, and the WagonR used in both the murders was recovered along with some fake ID cards, police uniform and several other incriminating material.