I'm not sure what you mean by torture....
if you're talking about more blatant physical methods....shocking grasp on genitals, sharps, blunts, racking, pressing, water or some such.....I would do physical saves and will saves, maybe something with Sense Motive and Intimidate.
If the PCs have the time, I would recommend more esoteric methods...sensory deprivation, time dilation, time distortion...these methods don't involve the immediate inflicting of pain but are designed to wear down the victim over time so that their mental faculties and will to resist are sapped to the point where they are more malleable and susceptible to coersion and questioning. But the PCs may not have the time to do this.