Thursday's hearing for confirmation of the charges is a test for prosecutors who must convince judges that their case, hastily reinvestigated since Ongwen's surrender last January after years on the run, is strong enough to merit a trial.
Prosecutor Ben Gumpert told judges Kony found children easiest to shape by a process of brutalization into the fighters he needed. Ongwen, by turns generous and cruel, played a role in this.
“Witnesses tell of how he instructed his personal escorts to administer dreadful beatings and ... even, on at least one occasion to kill, cook and eat civilians who had been abducted in attacks,” he said.
Ongwen had led attacks on four displaced-persons camps into which civilians had been driven by the Lord's Resistance Army's bloody campaign. Many were killed, and others were kidnapped and made to carry away the loot.
Nursing mothers who could not keep up had their babies torn from them and left behind in the bush, he said. A video taken by Ugandan authorities showed thatched huts burned to the ground and bodies in shallow graves in the aftermath of an attack.
Kony was indicted by the court in 2005 and remains one of the world's most notorious fugitives from justice. Several other indicted members of the group, which rose against Ugandan President Yoweri Musuveni in the late 1980s, are believed dead.
Ongwen, born in 1975, was visibly ill at ease in an environment very different from that in which he had spent his life after being abducted as a child, rising to say he did not need to hear the charge sheet.
“It is all going to be a waste of time,” he said.
Gumpert said Ongwen's own traumatic childhood could at most be a mitigating circumstance at sentencing. “Child abusers are overwhelmingly likely to have been abused themselves as children,” he said.
Lawyers for Ongwen, who pleads not guilty, will argue for the charges to be dropped next week.