Georgia political scientist Andrew B. Whitford and Kansas political scientistHolonna L. Ochs posted an empirical study called The Political Roots of Executive Clemency to SSRN.  The abstract: It is a widespread conventional wisdom that presidential pardons – the onlyway for offenders to remove or eliminate all disabilities that arise from afederal or military offense – are political. We move beyond this belief andassess the relative contribution of the president’s own policy agenda, otherpolicy agendas present in the separated powers system, and external socialconditions on the president’s dispensation of federal pardons. We estimate atime series model of the president’s aggregate dispensation of clemencyappeals (requests for pardons) and find that the probability of denials forexecutive clemency reflects the president’s own agenda and ideologicalposition. We show that evidence appearing to support direct effects ofCongressional attention to criminal justice issues and the homicide rate isspurious. In sum, while the president dispenses pardons as part of a systemof separated powers, how he exercises this unilateral power depends mostlyon his own policy positions. Paper here:
http://papers.ssrn.com/sol3/papers.cfm?abstract_id=888579