Happy at the conviction of four persons in the Shivani Bhatnagar case, senior IPS officer U K Katna, who headed the probe, said the court ruling proved that investigation had been done in a scientific manner.

"The conviction speaks of quality of investigation carried out," said Katna, Director General (Home Guards) who had supervised the probe as Joint Commissioner (Crime) in Delhi Police.

His comment came after a Delhi court convicted suspended Inspector General of Police R K Sharma and three others for the murder of journalist Shivani Bhatnagar, committed nine years ago.

"I am satisfied that the quality of investigation has proved of high order. Conviction is a result of quality investigation," Katna said.

Describing himself as a "satisfied" man, Katna said the Crime Branch had "systematically gone into all aspects of the case and evidence has stood the scrutiny of court".

He had special words of appreciation for late ACP Hemant Kumar who went into the telephone call details which proved crucial in the probe.

"Despite delay in working out the case, the Crime Branch team had adopted scientific approach in available circumstantial evidence," he said, adding "we never worked to shield anybody or implicate anybody".

The conviction in Shivani Bhatnagar case is the second high-profile investigation that Katna has handled successfully. Another such case was re-opened probe in the Jessica Lal [Images] murder, which also resulted in convictions.