The phrase "exhaustive investigation" means a very thorough and complete examination or analysis of something, leaving no stone unturned and considering all possible aspects or details. Full definition
The Council on Accreditation completed an extensive and exhaustive investigation of the practices of Family Connections, Inc. to ensure that the Agency's services are complaint with Hague standards and that the Agency provides quality, ethical services that are in the best interest of children, protect children from exploitation, and ensure quality service to prospective adoptive families. (adoptfamilyconnections.org)
Duffy has spearheaded exhaustive investigations into election ballots cast by dead voters; local police departments acquiring grenade launchers, AK - 47s and armored tanks; rogue dollar - jitney buses; and the true cause of a massive fire that destroyed the Seaside Park boardwalk after Sandy. (pix11.com)
illustrate the difficulty of being sure one has the «right answer,» because data can be missing or in conflict, even after exhaustive investigation. (educationworld.com)