Not allowed to lie

To terrorists. [Link]

Per the rules, you're not permitted to lie.
Well, you can tell a number of specifically-defined lies. It tells you what lies are permitted. It's not as if a terrorist is going to get that list or anything and realize if an interrogator is telling Authorized Lie Number Three -- which is, and I'm not making this up, claiming to already "know everything" and parading about a deceptively thick dossier loaded with mostly-blank pages to convince a subject you have a fat file on him (did I mention I'm not making that up? That is one of the permissible lies) -- that a terrorist is going to recognize it as Authorized Lie Number Three.
But apart from not allowing any kind of bodily contact like a slap, or any kind of threat, or even any kind of lie except a couple of hoary old cop-lies that are so old few cops bother with them anymore -- yeah, the Army Field Manual is really all we need.

"The Army Field Manual is very, very restrictive in what it can do," said Michigan Rep. Pete Hoekstra, the top Republican on the House intelligence committee. "For high-value detainees, it's a joke. ... In theory, it sounds great." The guidelines are all psychological in nature. The methods include good cop-bad cop, the silent treatment, and a trick in which interrogators can pretend to be from another country.

The silent treatment.

I propose an extreme tactic (those with sensitive constitutions should read no further): The "I'm not touching you" tactic.