How has music been used to highlight the injustices of the penal system?

i've got to give a Presentation on the above question for a HND in pop music. i was thinking along the lines of ';Back home in derry'; or ';fields of athenry'; both irish trad, but there must be more, san quentin by Johnny Cash for example. Any ideas songs or Quotes would be fab thanksHow has music been used to highlight the injustices of the penal system?
Bob Dylan 'The Hurricane'; The story of Rubin 'Hurricane' Carter, the black fighter wrongly convicted of robbery and murder.How has music been used to highlight the injustices of the penal system?
Johnny Cash song is Folsom Prison Blues. Peter Tosh has a lot of those type of songs. He is a Rastafarian