My first potential final outcome is an installation consisting of multiple shoeboxes, each one representing a Death Row cell. The audience will be able to look into the shoeboxes through two peepholes and see a different aspect of death row life in each one. Representing the cells as shoeboxes emphasises the lack of space that the prisoners are given, and letting people peek into them represents the lack of privacy and dignity that they're able to have.
My second potential final outcome is a recreation of the birdseye view of a Death Row prison, downsized to scale and built using shoeboxes / cardboard scraps. Building the entire prison on a scale small enough that people can walk around it and look down upon it emphasises the vulnerable position that the prisoners are in, and gives the audience a sense of power, similar to that which the guards hold over the inmates.
My third potential final outcome is a visual representation of the prisoners' writings, using shoeboxes to create a font and experiment typographically. This could merge with potential outcome number one; the shoebox 'cells' could simply be layed out in a typographical format.
Additional idea: Any of the above installations could be accompanied by someone narrating the letters in the background while people look around so that the letters are incorporated physically rather than just conceptually, and the final piece can have more of a personal feel to it.