Some information is verifiable, once in hand, but not easily attainable. Think passwords. If such information were extracted from someone via torture, it would be a simple task to check whether it's true, or the person was just telling you whatever would make the pain stop.

Another tactic would be to extract known information alongside the unknown information. If the known information checks out, when the torture victim eventually breaks, then the unknown information is much more likely to also be accurate.