New Delhi: India's Supreme Court on Friday dismissed a death sentence plea for the killer of an Australian missionary and his two sons in 1999, ruling that a life sentence was sufficient punishment.

India's federal police had appealed for the maximum penalty for Dara Singh, convicted for setting alight the car of Graham Staines in which he and his two sons, aged eight and 10, died.

Staines was a Christian missionary who had worked for three decades with lepers when a Hindu extremist mob torched his vehicle in a remote village in the eastern state of Orissa.

Singh and another man who was found to have assisted, Mahendra Hembram, were convicted, while 11 other suspects were set free.

A two-man bench in the Supreme Court ruled Friday that the case against Singh was not "the rarest of the rare," which is the only justification for handing down the death penalty in India.

Hindu groups accused Staines of converting poor Hindus in Orissa to Christianity.

At the funeral for her husband and two sons, Graham Staines' widow Gladys Staines said, “I forgive them”.

"I cannot express that how I felt when I got the news of my husband and sons being burnt alive. I told my daughter Esther that though we had been left alone, we would forgive and my daughter replied, 'Yes, we will'."

Staines remembered her husband and sons,"during these ten years, there have been times of sadness, I feel sad that I do not have my husband to support me, to guard me, but these are just momentary emotions of sadness which also fill me with great hope, the hope of heaven".

The bench concluded with a plea for religious tolerance and understanding.

"There is no justification for interference in someone's belief by force or coercion on the premise that one religion is better than others," they said.