The Collaborative International Dictionary of English v.0.48:

Inculpable \In*cul"pa*ble\, a. [L. inculpabilis: cf. F.
   incupable.]
   Faultless; blameless; innocent. --South.
   [1913 Webster]

         An innocent and incupable piece of ignorance.
                                                  --Killingbeck.
   [1913 Webster]

WordNet (r) 3.0 (2006):

inculpable
    adj 1: free of guilt; not subject to blame; "has lived a
           blameless life"; "of irreproachable character"; "an
           unimpeachable reputation" [syn: blameless,
           inculpable, irreproachable, unimpeachable]

Moby Thesaurus II by Grady Ward, 1.0:

21 Moby Thesaurus words for "inculpable":
   above suspicion, blameless, clean, exemplary, faultless, guiltless,
   innocent, irreprehensible, irreproachable, irreprovable, pure,
   righteous, unarraignable, unblamable, unblameworthy, uncensurable,
   unexceptionable, unimpeachable, unindictable, unobjectionable,
   virtuous