The case had created a political flutter as the first accused B K Biju was on the personal staff of Electricity Minister Aryadan Muhammad and the block Congress committee secretary at the time of the murder.
The First Additional District Sessions Judge, who delivered the verdict, also slapped a fine of Rs 86,000 on Biju and Rs 41,000 on the second accused Shamsuddin.
The prosecution case was that Radha (48) was beaten and suffocated by the accused leading to her death at the party office on February 5, 2014.
According to prosecution, Biju was afraid of Radha revealing some of his personal secrets which he wanted to cover up.
The accused were charged with 302 (murder) and other sections of the Indian Penel Code.