Henry Okah is being tried in South Africa, where he now lives.
He's thought to be one of the main leaders of the Movement for the Emancipation of the Niger Deltao (MEND).
The group has claimed responsibilty for the attack which killed 12 people, and has threatened more.
In this Aljazeera exclusive, Yvonne Ndege reports from a MEND training camp in their heartland, the oil-rich Niger Delta.