Burkina Faso has asked France to declassify military documents about the killing of ex-President Thomas Sankara, a lawyer for his family has said.
A judge had made the request because efforts to get them through “political channels” had failed, the lawyer said.
France, the former colonial power, has not yet commented on the request.
Mr Sankara’s widow and supporters have repeatedly accused France of masterminding his 1987 killing because he was a Marxist revolutionary.
Mr Sankara’s assassination led to his second-in-command, Blaise Compaore, seizing power in a coup.
Mr Compaore steered Burkina Faso into a strong alliance with France, which retains close political, security and economic ties with many of its former colonies in Africa.
Burkina Faso opened an investigation into the killing after he was ousted from power in 2014 in a popular uprising.