Category 1, Confirmed knowledge
A. Identified by the enemy by name
B. Identified by reliable sources.
Received from releasee/escapee or
C. Reported by highly reliable intelligence sources
D. Identified through analysis of all-source intelligence.

Category 2, Suspect knowledge
A. Involved in the same incidents as individuals in Category 1.
B. Lost in areas or under conditions that they may
reasonably be expected to be known by the enemy.
C. Connected with an incident that was discussed
but not identified by name in the enemy news media, or
D. Probably identified through analysis of all-source intelligence.

Category 3, Doubtful knowledge
This category contains individuals whose loss incident
such that it is doubtful that the enemy would have knowledge
of the specific individuals.
(e.g., aircrews lost over water or remote areas.)

Category 4, Unknown Knowledge
A. Individuals whose time and place of incident are unknown
(e.g., aircrews members downed at the unknown locations or ground personnel
that were separated from their units at an unknown time or place),
and B. Who do not meet criteria of categories 1 through 3.

Category 5, Category unrelated to degree of enemy knowledge.
A. Individuals whose remains have been determined to be nonrecoverable
as outlined in Department of the Army Technical Manual 10-286,
January 1964, section 39.
Data from Defense Intelligence Agency -- 20, January 1982