While working as a law clerk in the Augusta prison law library, I have had the privilege of assisting Rojai Lavar Fentress with fighting for his actual innocence. He has been incarcerated since the age of 15 for over 19 years for a murder that he didn't commit. He received new evidence in the form of an affidavit from the actual perpetrator of the crime, as well as evidence showing that the star witness identified someone else. The affidavit had to withstand the test for reliability that is done by judges to authenticate the evidence as new and reliable. In these cases the judge uses his discretion to determine the reliability.
A friend of ours found out from a clerk of the judge assigned to the case something that I will never forget. She said, "Fairness is due process, and justice is judicial discretion." This in essence means that as long as you receive due process (all correct procedures are followed) throughout your prosecution you are said to have had a "fair" trial, but just because its fair does not mean that justice has been done. The Judge can abuse his discretion, and deprive you of justice. Needless to say, the Judge in Rojai's case found the affidavit unreliable even though there is evidence that the witness identified someone else. I guess justice is judicial discretion; its all about whether the judge feels as though you deserve it, not what is actually just.