Here is an article about the link between poor literacy and crime:
http://www.timesonline.co.uk/tol/news/uk/education/article5513297.ece
I originally got involved in literacy through working in the Shannon Trust, which gets literate prison inmates to teach their fellow prisoners how to read:
Around 67% of prison inmates cannot read and we find they can often learn in just 4-5 months. The effect on them is massive and confirms the fundamental psychological impact that failing to learn to read at school can have.
– David