The Collaborative International Dictionary of English v.0.48:

Examiner \Ex*am"in*er\, 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.
   [1913 Webster]

WordNet (r) 3.0 (2006):

examiner
    n 1: someone who administers a test to determine your
         qualifications [syn: examiner, tester, quizzer]
    2: an investigator who observes carefully; "the examiner
       searched for clues" [syn: examiner, inspector]

Moby Thesaurus II by Grady Ward, 1.0:

34 Moby Thesaurus words for "examiner":
   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