exculpate \EK-skuhl-payt; ek-SKUHL-payt\ (transitive verb) - To clear from alleged fault or guilt; to prove to be guiltless; to relieve of blame; to acquit.
"Thus, she would have had to exculpate herself, and what I wanted was for her to exculpate herself. I already realized that I should have believed whatever reasons she had given me, and anything was better than not to see her again." -- Alexandre Dumas Fils, 'Camille'
Exculpate is ultimately derived from Latin ex-, "without" + culpare, "to blame," from culpa, "blame, fault."