Colonel Mike Mikombe, the ex-commander of the elite Republican Guard in Goma city, was accused of giving orders to open fire on anti-UN protesters.
His lawyers said he would appeal against the military court’s ruling.
This was the highest number of deaths in a crackdown on protests against UN peacekeepers in eastern DR Congo.
The protesters were demanding the withdrawal of UN troops, accusing them of failing to protect civilians who have been under decades-long attacks by rebel groups in the region.
The UN has almost eighteen thousand personnel in the country, including more than twelve thousand soldiers, making it the second-largest UN mission globally.
