Damn Paul, that was a very compelling argument for something I really hadn't thought about too much.  Your case makes awful lot of sense to me. 

I am curious about one thing however.  I was reminded of something that one of my college biology professors told us once.  He said that usually scientists perform their studies on specimens that have been removed from their natural environments and that that in and of itself necessarily clouds the conclusions that they might reach. 

The point I'm trying to make is that I would think that it would be difficult enough just to try to get your arms around a madman's thoughts, let alone after he's/she's been subjected to an environment that even a sane person would abhore. I'm not saying that your wrong at all, because you really did make an excellent point.  I'm just wondering how you would actually know that you are witnessing the true thoughts of the individual when they're caged like an animal and treated as such?

NOTE: be assured that I am not condoning allowing criminals to remain in their natural environment!  I'm just wondering how someone in this line of work deals with that aspect of their investigation.