None of the Geneva Conventions actually say this. OTOH, torture is subject to a universal prohibition under international law independently of the status of the tortured person, whether a protected person under the any of the Geneva Conventions, a regular criminal suspect in a domestic court system, or any other status that may or may not exist.
>None of the Geneva Conventions actually say this.
One way or the other it is mentioned in various places through the Conventions. In particular http://en.wikipedia.org/wiki/Third_Geneva_Convention :
for internal conflict
" The passing of sentences must also be pronounced by a regularly constituted court, affording all the judicial guarantees which are recognised as indispensable by civilised peoples. "
for international:
"It also specifies that when there is any doubt whether a combatant belongs to the categories in article 4, they should be treated as such until their status has been determined by a competent tribunal."
Geneva Convention states clearly - either POW status or suspect in the judicial system. There is no 3rd option.
> This is the conversation we should be having in my opinion.
there is no conversation to have. Only charges (of crimes against humanity which torture is) to bring in.