What is the current state of the law on the right of an inmate to present evidence at a disciplinary hearing?

"Generally, an inmate is allowed to present witnesses and documentary evidence when to do so does not threaten institutional safety or correctional goals." Zimmerlee, 831 F.2d at 187; see Wolff v. McDonnell, 418 U.S. 539, 566 (1974). Prison officials may exercise the necessary discretion to keep a hearing within reasonable limits and to refuse to call witnesses based on irrelevance, lack of necessity, or the hazards presented in individual cases. See Wolff, 418 U.S. at 566.