Some of the more damning parts:
>"Of the students tested, 81% accurately figured out the experimenter’s hypothesis (that guards would be aggressive and that prisoners would revolt or comply), and 90% predicted that the guards would be “oppressive, hostile, aggressive, humiliating” (p. 158), thereby supporting the argument that demand characteristics were likely operating in the SPE and that the participants in the SPE would have probably guessed how Zimbardo and his coexperimenters wanted them to behave."
>"Reason 4: The experimenters intervened directly in the experiment, either to give precise instructions, to recall the purposes of the experiment, or to set a general direction. "
>"When he began to get interested in prisons, only 3 months before the beginning of the experiment, Zimbardo already had strong views on the subject. As he would confide later, “my sympathies were heavily with prisoners. I was anti-prisons, anti-corrections, etc.” (Zimbardo, 2009, p. 34)."