Why shouldn't torture be justified for national security?
The primary arguments against the use of torture to defend national security are that torture is immoral and that it is ineffective. First, one may--depending on his belief-system--argue that torture is immoral because it violates human rights and exhibits cruelty to the prisoner.
Second, there is a strong case that torture is ineffective at preventing terrorist attacks. Research into enhanced interrogation techniques indicates that torture does not produce reliable evidence. As the above-cited article references, the CIA has even admitted its torture practices have not prevented terrorist attacks. Consequently, former CIA officer Glenn Carle asserts:
Torture does not work, it is illegal, and the professional intelligence, military, and law-enforcement officers who know what they are talking about, and who have firsthand experience, have been explicit that enhanced interrogation techniques undermine operational success.
Torture coerces prisoners into talking, but it is nearly impossible to determine whether or not they are telling the truth. Even body language reading is ineffective, according to recent scientific research. For these reasons, one can make a very good case that torture should not be used to defend national security.