Contrary to the movies, you don't tell them what you know about them so that they'll know when to lie.
It's a comforting fantasy that we can round up the bad guys, put them in a box and rough them up in clever ways until they reveal their evil plans. In the real world, building more Guantanamo Bays isn't going to solve any of the problems facing us. The net benefit of torture centers is negative.
To say it produces nothing just isn't true.
How do you know? Do you actually have any evidence that torture works?
pavlov provided a source above explaining that there is no evidence that torture is effective. Your response seems to just be "well they must just not be doing it right".
As an aside, I see a lot of parallels between this particular statement and the recent discussions on plea deals:
"They may say anything to make the waterboarding stop, and could actually be physically unable to provide any cogent intelligence."
Obviously the physical issues (probably) don't apply, but the use of oversized charges could be seen as a mental torture technique when phrased that way...
http://www.politifact.com/florida/statements/2016/may/24/tod...
"While many top officials defended the CIA’s use of waterboarding in the past, there is no irrefutable evidence the practice provides results. Experts said there are few historical accounts of success, and even those are suspect. Meanwhile, there’s scientific proof that a technique like waterboarding would affect brain function enough to make any prisoner’s statements unreliable. They may say anything to make the waterboarding stop, and could actually be physically unable to provide any cogent intelligence.
"Wilcox didn’t provide concrete proof and experts say virtually none exists. We rate the statement False."