This is Bill Vallicella's treatment of the issue of torture. I think that we can justify a virtual, though not absolute, ban on torture by requiring that, if torture is justified, we must have good reason before we do it to suppose that we will get accurate information for the person being tortured the value of which will outweigh any harm we do by torturing, and that there is no other way to get that information. But don't most torture victims just say anything they have to say to get it stopped, accurate or not? (That's what I'd do. I'd tell my captors what I thought they wanted to hear, not the truth). Experts on interrogations say that torture is not effective. And counting the cost is not as easy as it looks either. If we are to defeat terrorism we have to enlist the support of "moderate" Muslims to condemn the terrorists. How does it contribute to that goal if we start acting like the evil people they have always been told we are?
IF we really do have good consequentialist reasons to torture someone, then the deontologist-teleologist battle is joined. But first the above-mentioned epistemic difficulties must be surmounted, and to be honest I do not see how they possibly can be.