Innocence

I assume you're familiar with the Innocence Project. That's the one where wrongly convicted prisoners are freed after many years because new DNA techniques become available. Many of these people were freed from death row. This, rightfully, makes a lot of people celebrate. But why does noone talk about the elephant in the room.

Let U be the number of cases where DNA evidence does not become available.
Let D be the number of cases where DNA evidence becomes available.
Let E be the number of cases among D where the new DNA evidence exonerates the suspect.

Then we might expect that U * E / D prisoners will serve their full sentences for crimes they didn't commit. If we apply this reasoning to the death penalty, we will find a virtual statistical certainty that we have executed some number of innocent people. We just don't know which ones they are.

In this way, the emergence of a revolutionary type of evidence provides a statistical window onto the health of the justice system in general. Unfortunately, it is a temporary window. 20 years from now, there will be no more cases where there is unanalyzed DNA evidence. And I would argue that a technique this revolutionary is a singular event, and will not be repeated anytime soon. And if the elephant continues to be ignored and the present system is not fixed, then there will be no longer be an easy way to demonstrate it is broken.