The zone of truth spell allows a Will save, and to my understanding, a caster knows wether or not a character makes his saving throw against a spell that he casts (i.e. you can't just pretend to be charmed by charm person and 'go along' with it until you spot a chance to betray the caster).
That being the case, the zone of truth spell seems to take most or all of the oomph out of "murder mystery" and "court trial" plot devices. A third-level cleric (PC or NPC) could serve as an infalliable judge.
Any thoughts or simple ways around this?
I have never played with the caster knowing if a save is made. Is that in the rules somewhere?
As for it ruining plots, yeah, it does. Same with speak with dead and a couple other spells.
Someone casting or having cast protection from X on them is a good way to answer. You are effected by the spell, but are immune for the duration of your protection spell.
So if i have a ring of protection from good on (or have the spell cast on me), the good cleric casts zone of truth, i can actually intentionally fail my will save against the zone of truth, but be uneffected by it so long as i am affected by protection from good.
But yes, your standard murder mystery is not really a good plot line in dnd. Divination magic makes common thugs and such pretty much sitting ducks for PC's in terms of investigation.
Huh. Well, Caineach's question actually helped me to answer mine.
Succeeding on a Saving Throw: A creature that successfully saves against a spell that has no obvious physical effects feels a hostile force or a tingle, but cannot deduce the exact nature of the attack. Likewise, if a creature's saving throw succeeds against a targeted spell, you sense that the spell has failed. You do not sense when creatures succeed on saves against effect and area spells.
I guess that's that! ZoT is an area spell; murder trial is a go.
Zone of Truth is sort of a buzz kill for murder mystery campaigns, but I like to think that in a world where such a spell is possible, it is equally possible that the murderer has gone to certain lengths to ensure such magical retorts aren't always as effective.
Naturally, this is always a tough call, since you don't want to discourage players who preemptively picked the spell, but if you want players to get a little more gritty, it might be safe to assume some counter-magic was in place.
Just some food for thought!
Also, potion of glibness or the spell.