i see this as someone who's deeply stuck in a situation from where there's no escape. i don't think this is about prison though... it's just that sometimes we create situations or find ourselves in situations from which ther eis no escape... (but really, i think you should work on the typos - it mars an otherwise great write )
I see two things here. The first, the obvious, a man in prison, and his inability to escape. The second however is a little more subtle, and has to do with language you use to indicate that this imprisonment won't last forever. Particularly:
No escape Mortal walls to thick A finite story
You make a point of calling the walls mortal, which could mean a few things but you clarify by saying "a finite story" telling the reader that it will one day end. The prisoner is there for "45 to life" which tells us that the end may be in death, or in a very late release. I'm reminded of the Shawshank Redemption. You also throw in a line about the system failing, completing the theme that a "mortal" prison fails in its purpose, though that purpose is left to the reader to decide.