The fact that "they can always detach themselves from it and answer a different question that they asks themselves within their mind" isn't so well known for the vast majority of people. This is medieval times, low education, even if with magic. I'd say only a small % of people would know about this trick, such as competent criminals, skilled law enforcers, or magic users.

On a failed save, a creature can't speak a deliberate lie while in the radius. Your example of Q: "Did you kill the king?" A: "I did not" (kill a chicken) is what every sensible person in the world would simply refer to as "A deliberate lie"

Where exactly did you get the idea that a character can detach themselves from the meaning of words and make statements that they complete mentally in their mind? That's either a piece of 5e ruling that I wasn't aware of, or an incredibly liberal interpretation of "the truth".

"any court would condemn immediately any resisting person" This really irritates me. That's the kind of thinking that says "taking the fifth is tantamount to admitting guilt". There are many reasons somebody might not want to answer police questions even if they didn't do the actual crime they're (allegedly) being questioned about, especially since once you've been subjected to the zone, you're stuck for it no matter WHAT questions they start asking.

I'm trying to understand which true statements are allowed, if some are not because of what they relate to. "I did not kill" (a chicken) is a true statements but it does not relate to the question he was asked. So if under the spell you don't have to relate to the exact formulation but also can't disregard it completely, how much of a question should you regard?

@Toma "I did not kill" and "I did not kill a chicken" are two different statements. From a formal-semantics point of view, the first one is generally taken to mean "I did not kill anyone or anything".

@Draconis ok. So is the correct interpretation of Zone of Truth truthful statements that relate to the question presented by someone else? In that case should the formulation be followed exactly, or if not, how much of the question should be regarded to test if a statement is true or not?

@Toma Relevance isn't what I'm talking about; my point is just that "I did not kill" is a false statement if you killed the king. The truth or falsehood of a statement, in the field of formal semantics, is based on *the words that you said*—not on any additional secret words you're imagining in your mind. You spoke the statement "I did not kill", and that statement is false (if you actually did kill the king).

@Toma perhaps you are imagining someone who is blind and deaf and has no idea that they were just asked a question, and was just thinking to themselves that they have not killed a chicken, and decided to say it out loud. That would indeed, not be a lie. However if the person on trial is aware of the context into which they are speaking, then "I did not" is a deliberate lie, no matter what they say inside their own head.

I'm curious where you're getting the "ask yourself a different question in your head" idea.

That's the best way to cheat on a lie detector test :)

"Furthermore, if such resistance could be willingly forgone, any court would condemn immediately any resisting person." That's some massive rights violations right there (why refuse a house search if you've got nothing to hide?), and prime material for a BBEG who goes around zone of truthing people and outright executing anyone who resists - without figuring out what they may or may not have been hiding.

I saw a comment that made the most sense, the truth is defined by 1) true statement 2) relays on the question that was asked (exact formulation).

Note that “I did not (kill a chicken)” would not work on a modern lie detector unless you had extensive training and experience. Most studies have shown that it takes over ten years to learn to beat a lie detector. The saving throw given in D&D is far more generous than real life.

I plead the fifth edition!

@Flater it's a "rights violation" only from a modern perspective - e.g. the US constitutional bill of rights essentially is a list of prohibitions for things that governments used to do legally. Historically in pre-modern times on Earth - and thus presumably also in the D&D world - there generally would be a societal consensus that accused do not necessarily have rights to refuse to testify, and that the courts have the right to extract testimony from commoners however they want, including torture; nobles would have more rights, but not a random party of foreigner wandering murderhobos.

You are aware that there are no such things as lie detectors? There are machines show your heartrate and maybe breathing to see if you are agitated while making a statement. This data can be interpreted to conclude whether you are lying (to arguable quality). All it takes is that you simply don't care about the whole thing and be a good liar. So you can lie without it affecting your body. Its the stress that lets you fail a lie detector not the question itself changing the question inside your head does not accomplish anything.

If the full question is to be regarded with exact formulation the spell becomes very OP and a deliberate attempt to hide the truth is almost anything other than the full truth as known to the one effected.

Now the question is, do true statements in regard to a question asked (full formulation) that are a result of the attempt of the one effected by Zone of Truth to not allow some of the truth to be spoken are to be considered a deliberate attempt to hide the truth or should they be regarded as speaking the truth because saying part of the truth regardless of motive is what the spell does.

Notice that most upvotes allow for the lie detector method, therefore do not compel someone to answer a certain question at all and affirm my claim that the spell is useless