exculpate

v. free from blame, declare innocent

Verb
1. pronounce not guilty of criminal charges; "The suspect was cleared of the murder charges"
(synonym) acquit, assoil, clear, discharge, exonerate
(hypernym) pronounce, label, judge
(hyponym) vindicate
(entail) judge
(derivation) exculpation

v. exculpate, free from blame, declare innocent

(v. t.)
To clear from alleged fault or guilt; to prove to be guiltless; to relieve of blame; to acquit.
  

Something that excuses or justifies a wrong action. - (read more on Exculpate)