Ngudjolo is accused of using child soldiers in a 2003 attack on a village in the vast central African country, killing 200 people.
French judge Bruno Cotte is to read his verdict at a public hearing against Ngudjolo, once one of the most important militia leaders in northeastern Democratic Republic of Congo's mineral-rich Ituri province.
Now 42, Ngudjolo faces seven war crimes charges including using child soldiers to fight in his militia and three crimes against humanity charges for the bloody massacre of 200 villagers at Bogoro village on February 23, 2003.
It is the first time the Hague-based ICC, the world's only permanent war crimes tribunal, will hand down a verdict for murder, rape and sexual slavery.
Summing up the case in May, the court's then deputy chief prosecutor Fatou Bensouda recounted witness testimony on how victims were burnt alive, babies smashed against walls and women forced to serve as sex slaves.
"Child soldiers are said to have attacked Bogoro village, killing civilians, destroying property and pillaging," a charge sheet summary states.
The attack by ethnic Lendu and Ngiti-based rebel armies on Bogoro was "intended to 'wipe out' or 'raze' (the) village by killing the predominantly Hema population," in order to secure Lendu and Ngiti control of the main route to Ituri's provincial capital Bunia, it added.
A former deserter from the old Zaire army (FAZ) in 1996, Ngudjolo became leader of the Lendu-based Nationalist Integrationist Front (FNI) rebel movement and "had ultimate control over FNI commanders."
If found guilty, he could face up to 30 years in jail, or, if the judges deem the case to be particularly severe, life behind bars. A sentencing hearing would come at a later date.
Ngudjolo, who pleaded not guilty at the start of his trial on November 24, 2009, told judges he learnt of the attack a few days after it happened during a "meeting with generals."
His job as a trained nurse was "of a humanitarian nature", Ngudjolo said, denying he was ever a militia member.
His ally Germain Katanga faces similar charges but that case will be handled at a later stage, judges said.
Ngudjolo was arrested by Congolese authorities and transferred to the ICC on October 17, 2007.
His main adversary, Hema former militia leader Thomas Lubanga, was sentenced in July to 14 years behind bars for using child soldiers in his own rebel army.
In 2003, DR Congo was just starting to emerge from a war that embroiled the armies of a half-dozen nations and the isolated east was rife with violent militia groups.
Clashes in Ituri province broke out in 1999, and devastated the region, said the indictment, leaving some 60 000 dead, according to non-government group tallies. – Sapa-AFP