The Collaborative International Dictionary of English v.0.48:

Impeachable \Im*peach"a*ble\, a.
   That may be impeached; liable to impeachment; chargeable with
   a crime.
   [1913 Webster]

         Owners of lands in fee simple are not impeachable for
         waste.                                   --Z. Swift.
   [1913 Webster]

Moby Thesaurus II by Grady Ward, 1.0:

22 Moby Thesaurus words for "impeachable":
   accusable, arraignable, at fault, blamable, blameworthy,
   censurable, chargeable, criminal, culpable, faulty, guilty,
   implicated, imputable, inculpated, indictable, involved,
   open to criticism, peccant, reprehensible, reproachable,
   reprovable, to blame