Third, there's considerable grey area with zone of truth, but it requires clever criminals who anticipate the threat of zone of truth early on. Duping others into unwittingly doing your dirty work, such as slipping poison into the chef's spice rack, can evade all but the most rigorous line of questioning during a zone of truth.
There's also psychological tactics you can employ, such as charming/memory-modifying/plain-old-manipulating a creature to believe they committed a crime, so when they say "yes I did" under zone of truth, that registers as truth because they believe it. A magical fall guy, if you will.
Why would the interrogator allow this? As soon as you start dodging and evading, they break one of your fingers and say "Answer yes or no." Repeat till you give a straight answer. You can break a lot of bones in 10 minutes. And then they just cast it again.I just read the spell description of zone of truth.
C'mon, every politician can talk for 10 minutes without neither telling truth nor lies.
(I'm often listening to a (for germany typically liberal) news radio station, there is almost never a clear yes or no from a politician to any question, but long tirades evading any clear answers...)
Why would the interrogator allow this? As soon as you start dodging and evading, they break one of your fingers and say "Answer yes or no." Repeat till you give a straight answer. You can break a lot of bones in 10 minutes. And then they just cast it again.
That's the real problem with zone of truth: It turns torture from a highly unreliable interrogation technique (the guy says what you want to hear, whether it's true or not) into a perfect one. Not the kind of incentives I like to set up for the ostensible good guys.
You are right, there are definitely problems verbally dodging in a zone of truth if the interrogators are "not so nice".
On the other hand:
torture is (in most opinions) considered evil.
Evil is prone to corruption.
Thus, if the city have evil guys among them for the dirty work, I'd say chances are not too bad at least some of them can somehow be bought.