The author enumerates the three most common situations in which the courts have required the prosecutor to offer immunity to defense witnesses: (1) to safeguard the defendant's right to essential exculpatory testimony; (2) where the use of the prosecutor's powers to grant immunity causes such distortion in the fact-finding process as to require granting immunity to defense witnesses; and (3) where immunity is required to remedy prosecutory misconduct such as the intimidation of witnesses. The use of the "missing witness" instruction to avoid reaching the constitutional issue is also discussed.
Bennett L. Gershman, The Prosecutor's Obligation to Grant Defense Witness Immunity, 24 Crim. L. Bull. 14 (1998), http://digitalcommons.pace.edu/lawfaculty/938/.