"While A1 (prime accused) Nalini's punishment was reduced to life imprisonment from death, why can't the same be applied to my son (Perarivalan) who is only 18th accused?" Arputham Ammal told reporters here.
She alleged her son was falsely implicated in the case and that he was not at all involved in the crime.
Suspecting conspiracy in the trial, she wanted to know why it was handled ''very secretly'' by the authorities. "After all, a former Prime Minister has been murdered. So what was the need to keep the investigation a secret?"
She also wanted to how there were exactly 13 Sri Lankan Tamils and 13 Indian Tamils of the 26 found guilty by a local court in Poonamallee in 1998."The same trend continued even in the final four awarded death sentence by Supreme Court. Two are Sri Lankan Tamils and two are Indian Tamils," she said.
"When the Investigating Officer Ragothaman himself in his book has said they are still clueless on who made the belt bomb, how can they hold my son guilty for buying a 9V battery which they allege was used to make the bomb"? she said.
Ammal said she planned to meet Chief Minister Jayalalithaa to plead her case as "she can understand a mother's feeling better". She also plans to picket against capital punishment.
The accused were arrested in 1991. The Supreme Court in 1999 confirmed the death sentence of the four, including Nalini, whose sentence was later commuted to life.
The death sentences of the three men--Murugan, Santhan and Perarivalan-- were confirmed by Supreme Court in 2000.
Nalini's capital punishment was commuted to life by the apex court. The three men and Nalini belonged to Liberation Tigers of Tamil Elam and were convicted for assassination of Rajiv Gandhi in Sriperumbudur in Tamil Nadu on May 21, 1991.
The three men, charged with criminal conspiracy and execution of the suicide attack plot, had filed a mercy petition before the President after the apex court confirmed the sentence.
The Home Ministry had sent its opinion on June 21, 2005, which was called back for review on February 23, 2011, and was re-submitted to the President on March 8 this year.