So justice is easy but truth is hard. 
It's hard to tell what's true. The boy/girl who says you're the one. The missing cookie from the jar. The bloody knife by the body.
But it's easy to do justice. Just do the process right.
And don't mix it up with the truth.
We mix it up all the time. We expect the criminal justice system, the civil courts, and student conduct codes at college and universities to reliably arrive at the truth through adherence to the right process. We think a fair trial and an impartial ear solves all.