Liberian ex-president Charles Taylor is set to hear a historic verdict on charges of arming Sierra Leone's rebels in return for "blood diamonds" in the 1990s.
The decision on Thursday will be the first ever judgement against a former head of state by an international court.
Taylor is on trial at the Special Court for Sierra Leone in The Hague, Netherlands. He is charged with 11 counts of war crimes and crimes against humanity.
Taylor, who was president of Liberia from 1997 to 2003, is accused of backing and giving orders to Revolutionary United Front (RUF) rebels in the 11-year civil war in neighbouring Sierra Leone that killed some 50,000 people.
The prosecution says the RUF undermined a ceasefire agreement in 1999, prolonging the war for another three years, and that Taylor financed their war effort from the proceeds of "blood diamonds" mined illegally in Sierra Leone.
"The Taylor verdict is a watershed moment, however it turns out," said Richard Dekker, head of the international justice programme at Human Rights Watch.
"As president, Taylor is believed to have been responsible for so much murder and mayhem which unfolded in Sierra Leone. His was a shadow that loomed across the region, in the Ivory Coast, in Sierra Leone and Liberia."
Taylor has denied the charges.
The courts have earlier convicted RUF fighters of crimes against humanity, including rape, torture and terrorism.
Civilians were mutilated during the conflict, their arms being cut off above the hand (known by fighters as "long sleeves") or above the elbow ("short sleeves").
Trial witnesses described seeing children and pregnant women being shot, disembowelled or mutilated in a process aimed at creating terror in the civilian population.
But the challenge was to link Taylor to these crimes.
"The accused never set foot in Sierra Leone when these crimes were being committed. He never directly, physically committed these crimes," Brenda Hollis, the court's chief prosecutor, told the Reuters news agency.
"In a domestic case, you have to prove there was a murder, we have the added level of proving linkage."
Whatever the verdict, the losing side is likely to appeal, meaning the trial could easily last for another six months.
If found guilty, Taylor would serve time in a British maximum security prison.