During an exam, an examiner can put to an ordinary student a question that may be quite difficult even for the best of the group. What if, for some reason, the examiner has a predetermined intention to fail or mark down someone no matter how good they may be on the subject? To achieve that, they start asking deliberately tricky, difficult questions and finally, achieve their goal.
What the examiner's approach to the student may be called (interested, biased, prejudiced?), and is there a word for the question which is supposed to fail most of the students (a stumper, a sticker?)?
What typical words and expressions, or idioms may help to describe this situation:
A. In in a conversation between close friends, one of whom flunked the exam because of very tricky questions he couldn't answer?
B. In an official complaint against the examiner? (What did he actually — formal proceedings let aside — do to fail the student?)