The justice system makes a mistake, perhaps failing to convict. This is not necessarily a bad thing: what if crime X were not illegal? How would the non-criminal have turned out? Positive results could be used to justify change, repealing that law. It may reveal other deeper things about society.
One way to institutionalize this idea is to decrease the statute of limitation for crimes. After N years, we get to know the truth.
We also might need a "Get out of jail free" dice roll for highly visible crimes for which it is otherwise unlikely the justice system would err.
I suspect our justice system is too punitive (probably causing the huge prison population).
Shocking, of course, is the idea of deliberately letting some horrible criminals get away with it.