FYI, I think the 4th Geneva Convention applies to civilians captured during an occupation after a war. Civilians includes soldiers who stop fighting.
So it seems Saddam might fit into either definition, however, because Saddam is clearly under suspiscion of actions hostile to the security of the occupying power (the US), the US appears to be able to delay the vesting of Saddam's full rights under the Geneva convention to preserve the security of the US occupation, although the US must treat Saddam with "humanity". Its looks pretty subjective as to when the US must give Saddam his full rights.
Part 1
Article 2
"The Convention shall also apply to all cases of partial or total occupation of the territory of a High Contracting Party, even if the said occupation meets with no armed resistance."
Article 5
"Where in occupied territory an individual protected person is detained as a spy or saboteur, or as a person under definite suspicion of activity hostile to the security of the Occupying Power, such person shall, in those cases where absolute military security so requires, be regarded as having forfeited rights of communication under the present Convention.
In each case, such persons shall nevertheless be treated with humanity and, in case of trial, shall not be deprived of the rights of fair and regular trial prescribed by the present Convention. They shall also be granted the full rights and privileges of a protected person under the present Convention at the earliest date consistent with security of State or Occupying Power."
4th Geneva text