Personnel Security Investigation
50 U.S.C. § 435b(a)(6) (2010) (Title 50—Chapter 15: National Security--Subchapter F: Access to Classified Information)
(a) Definitions. In this section:
(6) The term "personnel security investigation" means any investigation required for the purpose of determining the eligibility of any military, civilian, or government contractor personnel to access classified information.
Department of Defense Regulation 5240.1-R, Procedures Governing the Activities of DOD Intelligence Components that Affect U.S. Persons, § DL1.1.19 (Dec. 1982): Personnel Security Investigation
DL188.8.131.52. An inquiry into the activities of a person granted access to intelligence or other classified information; or a person who is being considered for access to intelligence or other classified information, including persons who are granted or may be granted access to facilities of DoD intelligence components; or a person to be assigned or retained in a position with sensitive duties.emsp [sic]; The investigation is designed to develop information pertaining to the suitability, eligibility, and trustworthiness of the individual with respect to loyalty, character, emotional stability and reliability.
DL184.108.40.206. Inquiries and other activities directed against DoD employees or members of a Military Service to determine the facts of possible voluntary or involuntary compromise of classified information by them.
DL220.127.116.11. The collection of information about or from military personnel in the course of tactical training exercises for security training purposes.