Penology is a branch of criminology that focuses on prison management and the treatment of offenders.
According to James T. Kirk, between the 2240s and 2260s, Doctor Tristan Adams had almost single-handedly done more to "revolutionize and humanize prisons and the treatment of prisoners than all the rest of Humanity had done in 40 centuries [prior]." Kirk explained to Leonard McCoy that he had "been to those penal colonies since they've begun following his methods, and they're not cages anymore," and in fact, "they're clean, decent hospitals for sick minds."
When the USS Enterprise visited Tantalus V in 2266, Kirk requested from McCoy someone in his department who had psychiatric and penology experience for inclusion in the landing party visit to the Tantalus Penal Colony. McCoy's choice was Doctor Helen Noel. (TOS: "Dagger of the Mind")