His lawyers raised 90 grounds for the appeal, alleging legal, procedural and factual errors in the conviction and sentence.
In the first part of a hearing Thursday, the appeals judges upheld all of Ongwen’s convictions.
“The appeals chamber rejects all the defense’s grounds of appeal and confirms unanimously the conviction decision,” Presiding Judge Luz del Carmen Ibáñez Carranza said.
She was due to deliver the appeals chamber’s decision on Ongwen’s appeal against his sentence later in the day.
Ongwen sat in court listening intently to the ruling through a headset.
Ongwen was himself abducted by the shadowy militia as a 9-year-old boy and transformed into a ruthless child soldier. At trial, his defense lawyers said his abduction and indoctrination in the LRA made Ongwen a “victim and not a victim and perpetrator at the same time.”
The appeals chamber rejected arguments that he was mentally unfit to be convicted and that he was under duress at the time of his offenses.
The Lord’s Resistance Army was formed by its leader, Joseph Kony, as an anti-government rebel force in Uganda. It was accused of widespread atrocities, including mass killings, mutilations, recruiting and using child soldiers, and keeping girls as sex slaves.
A military campaign forced the LRA out of Uganda in 2005, scattering its members across central Africa. Reports over the years have claimed that Kony was hiding in Sudan’s Darfur region or in a remote corner of Central African Republic, where LRA fighters continued to kill and abduct people during occasional village raids, and where Ongwen was arrested in 2015.
Kony, who is a fugitive from the International Criminal Court, became internationally notorious in 2012 when the U.S.-based advocacy group Invisible Children made a viral video highlighting the LRA’s crimes.
