The stanford prison experiment 

"Stanford Prison Experiment, a social psychology study in which college students became prisoners or guards in a simulated prison environment. The experiment, funded by the U.S. Office of Naval Research, took place at Stanford University in August 1971. It was intended to measure the effect of role-playing, labeling, and social expectations on behavior over a period of two weeks. However, mistreatment of prisoners escalated so alarmingly that principal investigator PhillipG. Zimbardo terminated the experiment after only six days."  

"How we went about testing these questions and what we found may astound you. Our planned two-week investigation into the psychology of prison life had to be ended after only six days because of what the situation was doing to the college students who participated. In only a few days, our guards became sadistic, and our prisoners became depressed and showed signs of extreme stress. Please read the story of what happened and what it tells us about the nature of human nature."

–Professor Philip G. Zimbardo

"What happens when you put good people in an evil place? Does humanity win over even, or does evil triumph? These are some of the questions we posed in this dramatic simulation of Prison life conducted in 1971 at Stanford University. "

Although the Stanford Prison Experiment didn't go nearly as planned, I think it was a very telling demonstration of what can happen to a lot of people's minds given the chance to hold, essentially, an unlimited amount of power over another human being that they feel is "less than". Even more alarming about this experiment is that this was a group of innocent College students whose lives collectively changed, no matter if you were put in the role of an officer or an inmate. Even as explained by one of the participants who was put in the position of an officer, it never dawned on him how his awful behavior was until he was pulled out of it and had time to reflect on the experiment. If everyday people, chosen at random to be put into these positions, can have this result, I think that it is a very clear indication of how power dynamics can play a significant role within "real world" Correctional facilities.