The Guardians by John Grisham

John Grisham has been involved in the Innocence Project and puts some of his experiences and knowledge to good use in The Guardians. When we think of righting an injustice our thoughts are that with new evidence (most often DNA) and a good research team an innocent person can be set free. But there is more at stake here and others who are quite happy with the initial outcome. Those whose careers could falter when it's discovered they have encouraged perjury testimony, those who have tampered with evidence and the guilty party of the crime who is happily carrying on their life knowing someone innocent is incarcerated for their misdeeds.
Of course, with all John Grisham books there is a thrilling element of danger and he weaves a story around several cases, throws in a drug cartel or two and corruption within  the police force.