What were allegations against Rajiv Gandhi assassination convict Perarivalan who is now a lawyer?

AG Perarivalan, a convict in Rajiv Gandhi assassination case and who has now enrolled himself as an advocate, was 19 when he was arrested in 1991. The allegation against Perarivalan was that he bought and supplied a nine-volt battery which was used to detonate bomb that killed Rajiv. A shopkeeper had testified that Perarivalan bought battery from his shop.