scrutineer

Short definition from Wiktionary

Noun

1. 1
   A person who scrutinises; a person responsible for scrutineering.
2. 2
   A poll-watcher.
3. 3
   A person who observes any process which requires rigorous oversight.

Verb

1. 1
   To scrutinise; to thoroughly check that an election is being run fairly, or that a vehicle meets the rules of a competition, etc.