Amid a raging debate on the issue of clemency for killers of Rajiv Gandhi, the main investigator in the 20-year-old case D R Karthikeyan says that he will be happy if the death penalty of the three accused is commuted to life sentence.

With the demand for commuting their death sentence becoming an emotive issue in Tamil Nadu, he suggested that Parliament should convene a special session to discuss the policy with regard to capital punishment as decisions taken on regional basis would set a dangerous precedent.

"I have nothing personal against them. I did my duty, let the government do their duty now. I will be happy if their death sentence is reduced to life imprisonment," Karthikeyan told PTI.

Karthikeyan was asked to take charge of the special investigation team, a day after Rajiv Gandhi's assassination on May 21, 1991. Within a year on May 20, 1992, a day before the first anniversary of the assassination, his team filed the charge-sheet naming 41 people as accused.

The former IPS officer said the commutation of Nalini Sreeharan's death sentence may help the other three accused, whose mercy petition has been rejected by president Pratibha Patil. The supreme court had sentenced Murugan, Santhan, Perarivalan and Nalini to death in 1999.

The Madras high court had recently granted an eight-week interim stay on the execution of the convicts which was scheduled for September 9.

"They have got a case, as one of the condemned prisoners' death sentence has been commuted to life. Moreover, they have been in jail for 20 years, and their mercy petitions have taken 11 years, which was a long period of uncertainty," he said.