We won't ever, as Kurtz will never share it (if he has any).
The prosecution has a duty to share exculpatory evidence with defense; the defense (obviously) has no duty to share incriminating evidence with the state.
The jury is there to find the truth.
The judge is there to oversee the process of finding the truth.
The state must share evidence that contradicts its case, as part of the truth process.
The defense has no obligation to seek the truth, only to avoid bald-faced completely obvious false evidence.
That and the high burden of proof are part of the balance, but keep it in mind when the defense throws out some interesting theories unburdened by facts.