You seem to argue strongly in favor of deception, but justifying that it's ok if all the other measures against false convictions are in place (lawyers, police who work by the book...).
To me, it's like wearing a safety belt. I mean, if all your driver assistance systems work and all the other drivers pay attention and drive perfectly, you shouldn't need it, right?
I think the court reviewing the confession and tape of the interrogation would be the safety belt. There are ways to verify confessions even with limited evidence. These false confessions are sloppy work. It seems the courts don't care much for safeguarding against abuses, so maybe the verification steps need some codifying.
There also needs to be some utility left to the interview. Sure we don't want to have long, aggressive, or abusive interviews. But how useful would suspect interviews be if you just asked questions based on real information? Sometimes you might get some info, but the smart ones won't be that easy. Sometimes it would be good to use some deception just to gauge what they know, even if you don't get a confession. It's a useful tool that doesn't present any downside with the proper safety measures in place.
To me, it's like wearing a safety belt. I mean, if all your driver assistance systems work and all the other drivers pay attention and drive perfectly, you shouldn't need it, right?