“An “F” rating does not necessarily mean that the source cannot be trusted, but that there is no reporting history and therefore no basis for making a determination.”Headquarters, Department of the Army (SUA) · FM 2-22.3 Human Intelligence Collector Operations · 2006 · FM 2-22.3 «Human Intelligence Collector Operations» (6 septembrie 2006), anexa B «Source and Information Reliability Matrix», paragraful B-1
A source's reputation does not confirm the information, and a lack of track record does not refute it.
Every report gets two grades, not one. The letter, from A to F, says how reliable the source is, judged on what it has reported before: A reliable, B usually reliable, C fairly reliable, D not usually reliable, E unreliable, and F cannot be judged, for a source with no track record. The figure, from 1 to 6, says how credible the information in this particular report is: 1 confirmed by other independent sources, 2 probably true, 3 possibly true, 4 doubtfully true, 5 improbable, and 6 cannot be judged. The grid is known as the Admiralty code, after its British origin, and the same logic of two separate grades appears in NATO intelligence doctrine. In practice: grade the source on what it has delivered so far, then the information on what it says now — internal logic, corroboration, consistency with everything else. The grades are kept apart because they can diverge: a B source can send a 5 report, and a new F source can bring something already confirmed. The method pays wherever many heterogeneous sources flow in, open sources included. The traps: reading F as liar — the manual says explicitly it only means no track record — and letting the source's reputation contaminate the grade of the information.
Why it matters A single grade mixes two different questions and hides exactly the dangerous case: the good source that, this time, is wrong.