Must a priest who thinks he cannot judge a pennitent's sins impartially recuse himself?

The priest acts as a judge in the confessional. Civil judges must recuse themselves if they think they cannot judge a case fairly (because, e.g., they have conflicting interests, lack the requisite knowledge to judge a particular case correctly, etc.). Must a priest, who otherwise has faculties to hear confessions, recuse himself if he cannot judge a penitent's sins impartially? I am not asking if a priest can deny someone absolution or refuse to hear confession (because, e.g., of improper time and place). My question is more along the lines of 1983 CIC 977 , but not restricted to cases that involve sins against the 6th and 9th Commandments.