The Supreme Court ordered the release of one of the seven people convicted of involvement in the 1991 murder of former prime minister Rajiv Gandhi.
AG Perarivalan had spent over 30 years in jail. In 1998, he was given a death sentence, but it was later commuted.
Arrested at the age of 19, Perarivalan was convicted of procuring batteries that were used in the bomb to kill Rajiv Gandhi.
The ex-PM was assassinated by a female suicide bomber as he addressed an election rally in Tamil Nadu.
Rajiv's killing was widely seen as retaliation for his having sent Indian peacekeepers to Sri Lanka in 1987 when he was prime minister.
Perarivalan was a supporter of the Liberation Tigers of Tamil Eelam, which a rebel group fighting for a separate Tamil state in Sri Lanka. The rebels were finally defeated by Sri Lankan troops in 2009.
Perarivalan -- one of the seven convicts and his mother Arputhammal met Tamil Nadu Chief Minister MK Stalin in Chennai soon after the release.
The release of Rajiv Gandhi's killers is one of the key common grounds between the DMK and its political rival AIADMK in view of the sensitivities on the subject in the southern state.
The cause of the Lankan Tamils has always generated sympathy given the state's long tradition of identity-based Dravidian politics.
In its last manifesto ahead of the state elections, the DMK had promised to set free the seven convicts in the assassination case once it comes to power.
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