D&D 5E Detect Thoughts as an interrogation tool

[billd91]

Questions verbally directed at the target creature naturally shape the course of its thoughts, so this spell is particularly effective as part of an interrogation.

Yep, so I'm inclined to give the interrogation the benefit of the doubt and give up information as it comes up in the target's mind, unbidden.
That said, the target does know they're being probed and can take an action to try to expel the unwanted mental eavesdropper. So the spell may be effective for a while, but may not be counted on for long. So, ask the important questions right up front rather than trusting to maintain the connection.

 

[Nebulous]

Familiars can be pretty cunning, and this one knows its way around magic. It could certainly think false thoughts because it suspects this would throw the PCs off. Bonus is the PCs are likely to think the familiar isn't cunning enough to misdirect like that, and if they do - well good on them!

It's not a familiar; it's a wizard. I said earlier it was a wizard "familiar" with magic, as in acquainted.

 

[Nebulous]

I will offer a bit more detail for people. Remember, I'm trying to figure out for myself and my players (them especially) what is the fine line between surface thoughts and probing thoughts. Once they dig deeper the spell can end with a Wis save and/or Int. Just probing too deep ends the spell.

1) What is the chain of command in your organization? 2) Who do you report to?

Merely asking the question provokes a mental image in the interrogee. If you say "Don't think of pink elephants" you would instantly think of a pink elephant. The wizard doesn't want to divulge any of this, but the players are saying that their line of questioning evokes a surface thought the spell picks up on. I'm just trying to find some clarification so that as the group moves forward we're on the same page. The player himself wanted to make sure we're doing it right.

 

[Kobold Avenger]

Yes, saying certain questions out loud might provoke something to appear in surface thoughts. In a modern context I might say, "What's the PIN for your bank card?" and it might pop up your mind.

 

[turnip_farmer]

The player himself wanted to make sure we're doing it right.

Ah, well. That's where you're going wrong. There is no right. Either the information is there in the surface thoughts because he's being reminded of it; his thoughts are distracted by something else and he's not really focusing on their questioning; or he's consciously focusing on something (like Umbran's nursery rhyme) to intentionally avoid this kind of approach. This is up to you to decide.

 

[prabe]

A couple of thoughts.

1) It kinda sounds as though you're wanting to run it as a set of opposed checks of some kind. That's ... plausible, especially since the subject knows the spell has been cast. I'd think there's be some sort of advantage (or maybe even Advantage) for being able to read the surface thoughts.

2) If this technique is well-known in the setting, it seems as though organizations wishing to remain covert will develop ways of working around it. Cut-outs, disguises, and similar approaches seem probable. If someone doesn't know who his boss is, he can't tell anyone.

Neither of those thought may be relevant to OP, of course.

 

[Mort]

I will offer a bit more detail for people. Remember, I'm trying to figure out for myself and my players (them especially) what is the fine line between surface thoughts and probing thoughts. Once they dig deeper the spell can end with a Wis save and/or Int. Just probing too deep ends the spell.

1) What is the chain of command in your organization? 2) Who do you report to?

Merely asking the question provokes a mental image in the interrogee. If you say "Don't think of pink elephants" you would instantly think of a pink elephant. The wizard doesn't want to divulge any of this, but the players are saying that their line of questioning evokes a surface thought the spell picks up on. I'm just trying to find some clarification so that as the group moves forward we're on the same page. The player himself wanted to make sure we're doing it right.

Ok:

1. So with surface thoughts - no WIS save in play yet;
2. The wizard knows/understands this kind of spell;

I would think the wizard is "on guard" and could very well interject false or misleading thoughts. Sure, normaly when you say "who's your boss" he might think it, but here he might very well misdirect and similar for other questions.

I still think the type of target matters. And a wizard, familiar with this magic - you believe at your own risk.

 

[Mort]

A couple of thoughts.

1) It kinda sounds as though you're wanting to run it as a set of opposed checks of some kind. That's ... plausible, especially since the subject knows the spell has been cast. I'd think there's be some sort of advantage (or maybe even Advantage) for being able to read the surface thoughts.

2) If this technique is well-known in the setting, it seems as though organizations wishing to remain covert will develop ways of working around it. Cut-outs, disguises, and similar approaches seem probable. If someone doesn't know who his boss is, he can't tell anyone.

Neither of those thought may be relevant to OP, of course.

That's true: This is exactly where skills like deception (for the WIzard) and insight, for the characters would come into play.

 

[Dausuul]

I ban this type of spell in my own games, but if I were running a campaign that allowed them, I would say a subject who is familiar with detect thoughts can "guard their thoughts," filling their minds with repetitive surface thoughts (per @Umbran) and forcing a save to get any information at all.

To prevent "I'm always guarding my thoughts!" I would rule that doing this requires your whole attention. Your ability to make conversation is limited to absent, automatic responses--anyone talking to you can easily tell that you aren't listening--and you have disadvantage on all ability checks.

(However, this is not concentration and cannot be disrupted like disrupting a spell. If you hurt somebody who's guarding their thoughts, it actually helps them, because now they can focus on the pain.)

 

[el-remmen]

Remember the duration is only concentration up to one minute, which is not very long for a contentious interrogation.