LOL, David. I hope you are at the front of the line.
Ceili, you might already have heard of the Stanford Experiment, but here is a link plus a copy and paste of the first couple of paragraphs:
http://en.wikipedia.org/wiki/Stanford_prison_experiment
The Stanford prison experiment was a study of the psychological effects of becoming a prisoner or prison guard. The experiment was conducted from Aug. 14 - 20, 1971 by a team of researchers led by Psychology professor Philip Zimbardo at Stanford University. Twenty-four students were selected out of 75 to play the prisoners and live in a mock prison in the basement of the Stanford psychology building. Roles were assigned randomly. The participants adapted to their roles well beyond what even Zimbardo himself expected, leading the "Officers" to display authoritarian measures and ultimately to subject some of the prisoners to torture. In turn, many of the prisoners developed passive attitudes and accepted physical abuse, and, at the request of the guards, readily inflicted punishment on other prisoners who attempted to stop it. The experiment even affected Zimbardo himself, who, in his capacity as "Prison Superintendent," lost sight of his role as psychologist and permitted the abuse to continue as though it were a real prison. Five of the prisoners were upset enough by the process to quit the experiment early, and the entire experiment was abruptly stopped after only six days. The experimental process and the results remain controversial. The entire experiment was filmed, with excerpts soon made publicly available.
This goes straight to your idea that the police mentality is contagious, as is mob mentality.