(n.) One who examines, tries, or inspects; one who interrogates; an officer or person charged with the duty of making an examination; as, an examiner of students for a degree; an examiner in chancery, in the patent office, etc.

analyst analyzer asker catechist cross-interrogator cross-questioner detective examinant inquirer inquisitionist inquisitor inspector interlocutor interpellator interrogator interrogatrix interviewer investigator observer opinion-sampler poller pollster prober querier querist questioner questionist quizzer sampler scrutineer secret agent tester visitator visitor