Can a spell caster tell if an area-of-effect spell affects a particular target.

[Kobolum]

Let me paint this scenario. My group and I were tasked with judging and sentencing a criminal alleged of theft. This criminal had been caught and punished twice in the past and this was the third time it happened.

Now in order to try and figure out the truth are inquisitor prepared several Zone of Truth spells. (I'm sure you can already see the problem.) When the spell was cast are inquisitor wanted to know if the spell was effective or not and our GM allowed it because when single-target spells are cast on someone you can tell if they're effective or not even if the spell doesn't have any visible way to tell if it worked.

My argument was that since it's an area-of-effect spell you shouldn't be able to tell because you're not targeting one person you're targeting an area.

[Fuzzy-Wuzzy]

I agree with you, but I can't actually cite rules text to that effect.

[Pizza Lord]

Magic: Saving Throws wrote:

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.

[Kristal Moonhand]

Have the Inquisitor instead use Abadar's Truthtelling. (It's called Touch of Truthtelling on the PFSRD.)