"Democracy cannot faction without the institution that nurtures a culture of participation and respect for justice," Louise Arbour said in the capital, Bujumbura, on Wednesday.
"This is where Burundi faces the greatest challenges," she told reporters. "Apart from a functioning executive and legislature, [it needs] a judiciary that would inspire confidence from the population; that would rule out impunity."
Arbour was on a five-day visit to Burundi, where she met government officials and civil society leaders, mainly from human rights associations.
She pointed to progress in the electoral process, participation of women in public life, media freedom and an opening of space for NGOs as positive developments. "The participation of women in public life is a sign of inclusion that should be celebrated," she said.
However, there was still fear of abuses among the Burundian population, she said, citing an incident in Muyinga where 30 people were murdered and dumped in a river in August 2006.
The attorney-general, Jean-Bosco Ndikumana, said the killings were perpetrated by unknown men. All the victims were members of the Forces national de libération, the rebel group.
Commenting on plans to set up a truth and reconciliation commission (TRC) and a related special court to focus on war crimes, crimes against humanity and other serious violations, Arbour said consensus was necessary. "The question is whether the prosecutor of the special court would be bound in any way by the TRC," she said. "This would be an important element of clarity in the pursuit of peace and reconciliation in Burundi."
President Pierre Nkurunziza and Arbour agreed that national consultations led by a tripartite committee be held on the matter. The committee will comprise nominees from the government, the UN and civil society.
"The national consultations will start in July 2007," the president said. "The setting-up of the TRC and the steps that will follow will depend on the will of the Burundian citizens."