1) Adjuster 2) Adjustor 3) Agent 4) Boffin 5) Coroner 6) Detective 7) Dick 8) Experimenter 9) Factfinder 10) Fieldworker 11) Gumshoe 12) Hawkshaw 13) Ombudsman 14) Plainclothesman 15) Prober 16) Researcher 17) Tec 18) Tracer 19) Wiesenthal 1) Australian magazine 2) Australian quarterly magazine 3) Man of science 4) Research worker 5) Researcher 6) Scientist 7) Someone who investigates 
• (n.) One who searches diligently into a subject.
(from the article `biology`) ...Banks, a young naturalist, with the opportunity to make a very extensive collection of plants and notes, which helped establish him as a leading ... [3 related articles]
A researcher in a clinical trial or clinical study.
a clinical researcher who is involved with a clinical trial protocol and its implementation. The Principal Investigator is ultimately responsible for the conduct of the trial.
In·ves'ti·ga`tor noun [ Latin : confer French investigateur .] One who searches diligently into a subject. 
[n] - someone who investigates
A researcher involved in a clinical study. Related terms include site principal investigator, site sub-investigator, study chair, study director, and study principal investigator.
[6th grade words] someone who inquires carefully