Investigator means an individual who actually conducts a clinical investigation (i.e., under whose immediate direction the drug is administered or dispensed to a subject). In the event an investigation is conducted by a team of individuals, the investigator is the responsible leader of the team. Subinvestigator includes any other individual member of that team.
21 CFR § 312.3
The definitions and interpretations of terms contained in section 201 of the Act apply to those terms when used in this part: