The ICC convicted Ongwen of 61 of the 70 charges against him.
The 45-year-old’s crimes include murder, torture, enslavement, rape, and forced pregnancies, the court said.
The case was the first at the ICC to involve an alleged perpetrator and victim of the same war crimes, with Ongwen himself having been abducted by the rebels as a child while on the way to school, according to his defense.
A former commander of LRA’s Sinia Brigade, Ongwen told the court he was abducted from his home by LRA fighters when he was 14.
“We recognize that there may be thought to be something of a paradox in the fact that the stories told by so many of the witnesses in this case could in other circumstances be the story of Dominic Ongwen himself,” prosecutor Benjamin Gumpert said during the trial.
“But this is no reason to expect that crimes can be committed with impunity. We have a choice as to how we behave, and when that choice is to kill, to rape and to enslave, we must expect to be held to account.”
“Today’s ruling remind me that there is something called justice,” said Jobson Obol, 42. He survived an LRA ambush on a bus in 1999 in which his father died.
“Ongwen is not the only one who was abducted as a child and forced in LRA ranks,” he told CNN in Uganda’s capital, Kampala.
“I have relatives and friends who were abducted and escaped… They were rehabilitated and forgiven by their own communities and families.”
Millicent Ayot, 38, lost her parents and four siblings in an LRA arson attack.
“The convicting of Ongwen serves some relief, but does not bring back lives lost,” she said. “We hope the court keeps him in jail for life.”
The court can sentence Ongwen to up to 30 years imprisonment, or a life sentence in certain circumstances, according to the Rome Statute, the ICC’s founding document.
The death penalty is not provided for.
Ongwen, nicknamed “White Ant”, is also the first LRA member to face justice at the tribunal in The Hague or anywhere else over the bloodshed that stretched across four African nations.
The court granted 4,095 victims the right to participate in the trial, which opened in December 2016, according to a press release.
The ICC’s chief prosecutor, Fatou Bensouda, presented 109 witnesses and experts. and the total cases record include more than 1,760 filings.