Department of Defense Regulation 5240.1-R, Procedures Governing the Activities of DOD Intelligence Components that Affect U.S. Persons, § DL1.1.22 (Dec. 1982): Reasonable Belief
A reasonable belief arises when the facts and circumstances are such that a reasonable person would hold the belief. Reasonable belief must rest on facts and circumstances that can be articulated; "hunches" or intuitions are not sufficient. Reasonable belief can be based on experience, training, and knowledge in foreign intelligence or counterintelligence work applied to facts and circumstances at hand, so that a trained and experienced "reasonable person" might hold a reasonable belief sufficient to satisfy this criterion when someone unfamiliar with foreign intelligence or counterintelligence work might not.