I am a utilitarian and basically believe, among any set of ethical choices, whatever outcome is likely to minimize human suffering ought to be pursued (well I do reserve some qualifications but thats a story for another day). Yes, determining that outcome in the first place is not an easy or exact process in the first place. On the other hand, people in this debate, usually sentimental folk, often seem to think that this means that the trade-off between possible suffering inflicted (say an innocent but nevertheless radical Muslim gets tortured) and suffering avoided (e.g. you torture a jihadist and get crucial information regarding some other jihadist plot) is therefore automatically too great for torture to be worth it.
The problem with this tacit assumption is that one can easily argue the same for the prosecution system in general: determining whether someone has committed murder or not and consequently giving them life imprisonment or worse isn't an exact judgement either, and inflicts possibly far more suffering (innocent people have their entire lives wasted in prison vs a few months torture). Of course the argument seems silly here because most people understand very well that in a competent judicial system, innocent people do not get framed and prosecuted for murder very often.
Absolute certainty is not a requisite for prosecution because we still have this very neat thing called evidence which makes it possible to have this other neat process called making a decision based on a (pretty accurate) probability, most of the time anyway. And we accept that the trade-off between possible suffering inflicted and suffering avoided in the case of prosecuting murderers is worth it because it is very small -that is, most of the time you prosecute murderers and not framed innocents etc.
Now the question is: when governments torture, to what extent are their suspicions evidentially based? I believe that competent governments as in the west, for example, do not go about torturing random people with no evidential suspicion. Now there is one other issue here, how effective is torture anyway? But thats an empirical question and not an ethical one.