The prisoners of Hadante were formerly inhabitants of Rillaan under the reign of the Taldor, a powerful body of governors and sentencers who, in closed quarters, made rash decisions based on crimes which, often, might have seemed unjustified to outsiders.
Still, the majority of the Hadante captives appear to be in for justified crimes, as their behavior tends to lend itself to an array of evils. One long-time inhabitant, Linea, was sentenced to Hadante for annihilating half of the population under the Taldur. Consequently, the prisoners yielded to her will out of fear, often serving her meals and allowing her to maintain her own living quarters where she continued her scientific endeavors.
Linea spoke of those who were in control in Hadante, and that one could either control a population by fear or by hope. To this end, she allowed the people to believe that there was hope on a life free from Hadante if they stood before the Stargate as the unstable energy vortex ignited, swallowing their bodies into the outburst of energy. Her victims often did this, perhaps not realizing they were sentencing themselves to oblivion and also an ultimately death as the wormhole completely consumed them, killing them as a result.
Linea and SG-1 escaped from Hadante utilizing Linea's Terra-root, which generated enough of an electrical charge to allow the inner track of Hadante's Stargate to unlock and spin freely, allowing a lock on P2A-509 where SG-3 could provide the team with a GDO. (SG1: "Prisoners")