person who investigates or checks something; examiner; investigator

A process where experts evaluate the work or research of others in the same field.

to investigate and verify the personal background and political history of a government or party official

investigation into an individual's political history or reliability, typically for employment or party membership in the People's Republic of China

To put someone in isolation while they are under investigation; a method of interrogation where a person is forbidden from contacting the outside world to prevent collaboration or evidence tampering.