I'd guess that the usual bell, book and candke, vicars and priests etc would exorcise a ghost whether you'd killed the person or not.
Whether you (ie one) can exorcise it from one's own memory would be more difficult.
Unless you felt no grief or remorse it wouls stay with you.
Even repentance would not lift the memory. You'd be stuck with it no matter how many bells and smells you empolyed to try to lift the stain.
Candke = candle. I should give up the ghost!