The case before the Hague-based ICC opened with presiding Judge Chile Eboe-Osuji asking Ruto, 46 and fellow accused, Kenyan radio boss Joshua arap Sang, 38, to enter pleas to three charges of crimes against humanity each. "Not guilty," both men told the judge.
Ruto arrived at the court voluntarily after flying in to The Hague from Nairobi to face charges of masterminding deadly post-election violence in the east African nation five years ago. A crowd of Kenyan MPs and other supporters welcomed Ruto and Sang as they arrived for the politically-charged trial that has also seen the court come under withering attack.
Kenyan President Uhuru Kenyatta, a one-time political foe of Ruto's turned ally, goes on trial at the ICC on November 12. He also says he is innocent.
Ruto, dressed in a grey suit and red and white tie, smiled as the ICC's chief prosecutor Fatou Bensouda opened her case, while Sang, in a light grey suit, lavender shirt and maroon tie shook his head and occasionally smiled.
"Mr Ruto, as a powerful politician" planned the crimes "to satisfy his thirst for political power," Bensouda told the court. "It is difficult to imagine the suffering or terror experienced by the men, women and children who were burnt alive, hacked to death or chased from their homes," Bensouda added. "Mr William Ruto and Mr Joshua arap Sang are most responsible for these crimes," she said.
The ICC has come under increased pressure globally, especially from the 54-nation African Union, which accused the court of targeting the continent on the basis of race and demanded the court drop the Kenyan prosecutions. The trial also comes just days after lawmakers in Kenya became the first in the world to approve moves to withdraw recognition of the court's jurisdiction.
Any move by Kenya to leave the ICC's Rome Statute will have no effect on the current trials, but observers fear it may spark an exodus of court member states in Africa, where all the ICC's current cases are based.
Ruto and Sang each face three counts of murder, deportation and persecution after a wave of violence swept Kenya in 2007-08, leaving at least 1,100 dead and more than 600,000 homeless. Violence in 2007-2008 laid bare simmering ethnic tensions. The violence was mainly directed at members of Kenya's largest Kikuyu tribe, who were perceived as supporters of then president Mwai Kibaki's Party of National Unity (PNU).
Pre-trial judges said evidence suggested that Ruto held a number of meeting to plan the ethnic killings as far back as December 2006. Initial attacks quickly led to reprisals, with homes torched and more people hacked to death, bringing some parts of the country to the brink of civil war.
The ICC, the world's only independent, permanent tribunal for war crimes, genocide and crimes against humanity, took charge of the cases after Nairobi failed to set up a tribunal of its own in line with agreements brokered by former UN secretary general Kofi Annan.
Despite vowing cooperation with the court, Kenyatta said over the weekend that he would not allow both leaders to be out of the country at the same time. Ruto and Kenyatta's trials are expected to be staggered, four weeks at a time, so that both men are not away from Kenya at the same time.
The cases have been mired in accusations of witness intimidation, allegations dismissed by the defence. But several witnesses already have pulled out of the trial and ICC prosecutor Bensouda and rights groups have frequently raised the issue. There is concern in Kenya that the trials could reopen old wounds and undo reconciliation efforts by communities who once fought each other in deadly battles.
By Guylain Gustave Moke
African Affairs Expert