When you take away the justice system - the police, the lawyers, the courts and the jails - and it’s just two groups facing each other with some terrible event coming between them, how do you do justice?
Is it about deciding on a suitable punishment? Is it about what’s fair for everyone? How can you possibly do justice for something as big as genocide?
John Steward, a consultant for World Vision, says that he has learnt a lot about justice by watching Rwandans rebuild their country. He believes that, at its most basic, the best justice has two elements.
"The first is where the offender faces what they have done," he says. "I mean that the perpetrator by nature runs away from their victim - they don't want to know them. So the first step of justice is for the offender to stop running away."
The second element of effective justice is where the offender starts thinking in terms of the victim. "They will say something like, 'I'm sorry for what I did and I want to do something for you - I want to repay you in some way for what you have lost'.
"Obviously, Rwandans can't replace life but they also damaged, stole and destroyed property. By replacing some of those physical things and also offering other kinds of support, they can go some way towards restoring everything that was taken away. I don't think justice is ever justice unless that takes place."