The International Criminal Court (ICC) in The Hague is set to deliver its first verdict, in the case of DR Congo's Thomas Lubanga.
Mr Lubanga is charged with recruiting and using child soldiers in north-eastern Congo in 2002 and 2003.
He has pleaded not guilty saying he was only a politician and was not involved in the violence.
But the prosecution has accused him of using children as young as nine as bodyguards, sex slaves and fighters.
During the trial videos were shown which appeared to show Mr Lubanga galvanising child soldiers to fight in the conflict between Hema and Lendu tribes in some of Africa's worst ever tribal warfare.
He does not deny that he led the Union of Congolese Patriots political group but insists he was not in charge of its armed wing.
The chief prosecutor at the ICC, Luis Moreno-Ocampo, told prosecutors: "The defendant stole the childhood of the victims by forcing them to kill and rape. Lubanga victimised the children before they ever had a chance to grow up."
Anneke Van Woudenberg of Human Rights Watch has been to the scene of the conflict, Ituri, many times where she said "more than 60,000 people were brutally slaughtered, where there was really ethnically targeted violence, mass rape, mass torture, mass arbitrary arrest".
After documenting Mr Lubanga's activities, she said she was hoping "that this verdict will start to see the process of justice begin".
The verdict in the Hague will be handed down by three judges and if Mr Lubanga is found guilty he will face a maximum sentence of life imprisonment. The court cannot impose the death penalty.
This is a landmark case for more than one reason. After the ICC was set up 10 years ago Mr Lubanga became the first suspect to be taken into their custody.
It is also the first international trial focussing on the use of child soldiers and it could set legal precedents for others accused of similar crimes.
And while international criminal tribunals for the former Yugoslavia and Rwanda only try crimes committed in those territories over a limited time and will eventually be wound up, the ICC is a permanent body.
Mr Lubanga is one of 20 suspects who have been the subject of arrest warrants from the ICC - others include Saif al-Islam Gaddafi, the son of the former Libyan leader, and several members of the Sudanese government, including President Omar al-Bashir.
The court has had to overcome many delays but Mr Moreno-Ocampo told the AFP news agency it had been a success
"When I started people said we could not do it, we would never have a case in court. We now investigate in seven countries, we have people in prison, we are a court."
The United States' first ambassador-at-large for war crimes, Prof David Scheffer, told the BBC's Today programme the court was still "in its baby steps".
"It does take an enormous amount of effort to bring complex war crimes cases to trial," he said.