The "criteria" is simply to not discrminate. That is, the inmate should be treated the same as other inmates who were incarcerated for the same offense, with similar prior criminal records and similar behavior in prison. If the inmate is treated differently than similarly situated inmates of different races, religions, etc., then there may be discrimination. Of course, since every situation is unique at least in part, it may be very difficult to show that a decision was made on improper discriminatory grounds, rather than based on some difference in the offense, sentence, post-conviction, behavior, or other legitimate grounds for treating this inmate differently than other inmates. It is a largely subjective decision.