Grace and Justice share one big common foundation: the recognition of guilt. Or sin if you want to be churchy about it. Without this, there can be no grace and no justice, for neither is needed.
Grace and Justice are, however, very different. Grace’s goal is growth. It is not simply the forgiveness of sins, but it is a process of elevating the sinner to a new state so that by the end of the process the one who started out guilty is something more than they ever were before. Justice, on the other hand, is about equality. Justice seeks only to restore equilibrium to the system. A wrong is committed that unbalances the system, justice seeks to redress the wrong to bring the system back to balance.
Again, in both cases, wrong must be acknowledged. The one who committed the wrong doesn’t have to acknowledge it, the one in a position to administer grace or justice must. Letting someone get away with a crime is not grace, it is injustice. For grace to occur the crime must be acknowledged, forgiven, and a process of restoration begun.
In most of the American history there has been no real drive for Justice in the so-called Justice system because we have misunderstood punishment as justice. Punishment is not justice, it gives wrong for wrong but does nothing to re-establish balance. Of course that assumes there was balance in the system from the start, which is not the case. Inherent inequities lead to crime, which leads to criminal injustice, which leads to punishment. Never creating balance at all.
We can get upset about specifics, and I am, but ultimately it just illustrates the need for radical reformation to create justice.
And just in case anyone feels that calling for justice is outside my purview, try reading the Bible, especially the prophets, and get back to me on that.