If an NPC is telling the truth, what's the Insight DC to know they're telling the truth?

[Satyrn]

If the NPC was a terrible truth teller, I'd set the DC as 10. If he was a great truth teller, it would be a 20.

 

[Satyrn]

But seriously, if I was setting the DC for an insight check to determine if the NPC was telling the truth, I'd set it at my default.

Anytime I set a DC, I start at 10, raising it only if it strikes me as a particularly difficult task.

If the person in question was an inveterate liar, that'd get me raising the DC to 15. Or if we're talking about a situation where lying is the expected norm and truth-telling is in short supply, like in a game of poker or Big Brother.

For an inveterate liar in the Big Brother house, the DC would be 20.

 

[Satyrn]

An inveterate liar playing poker in the Big Brother house is not telling the truth. No roll is needed to figure that out.

 

[Inchoroi]

If a PC asks to roll Insight against an NPC telling the truth, I say "you don't suspect he's lying" or "he seems to be telling the truth" - something along those lines - regardless of what the PC rolled.

Yep, this is how I do it. I also pre-roll all the NPCs deception rolls (unless I absolutely have to roll them during a session, when they surprise me with a question), so the players aren't tipped off by my rolling. Because of this, unless the roll assigned to that specific information for that PC is beaten by a PCs passive Insight or they make an active Insight check against it, they'll never know whether or not one of my NPCs has been lying to them.

Well, until its too late, anyway.

 

[abirdcall]

If a PC asks to roll Insight

I remind the player that they are to describe what they are doing and then the DM adjudicates.

There is no 'roll insight' in 5e.

If the player wants their character to study someone then adjudication is the same for everything else. success, failure, or random outcome.

 

[MarkB]

If a PC asks to roll Insight against an NPC telling the truth, I say "you don't suspect he's lying" or "he seems to be telling the truth" - something along those lines - regardless of what the PC rolled.

Which is going to totally mess with the mind of the player who rolls a 5.

 

[Hussar]

On a successful roll, I'll straight up tell the players that the NPC appears to be telling the truth. Only problem is, how do the players tell a successful roll vs a fail, which would also give the same answer.

Solution? Roll in the open. Let the players know that they succeeded. Let them know that they failed. A fail doesn't mean that the NPC is lying, just that the players don't know either way. A success, in my mind, should be an actual success. All this equivocating or "letting there be leeway for error" is just a player screw job AFAIC.

I mean, you don't do that for any other roll do you?

"You think you hit, but, you might not have. You maybe did 15 damage, but, you can't really tell."

"You figure that you climbed that wall, but, you cannot be sure."

"You think you are following those tracks, but, hey, until you actually do follow them, maybe you're wrong."

Yeah, I'm not big on playing silly buggers to try to increase difficulty. If the players succeeded on an Insight check, then, well, they succeeded. They discern the "true intentions" of the target creature. Seems straightforward to me. If they succeeded in an insight check, then they know that the NPC isn't lying to them. Note, that doesn't mean that the NPC can't be wrong and still deceive the PC's in some manner. But, why bother having a decent Insight if all it does is give me "probably right" answers?

 

[Bawylie]

I've been setting it as their 'Passive Deception' DC. What do you do?

I ask the player what the character is doing to determine whether or not the NPC is telling the truth and then determine the DC based on the approach.

 

[Imaculata]

And how does the DM make that decision? To me, it seems that is exactly what the Deception skill is intended for.

That seems to be a narrative decission to me. Some npc's are good liars and you can't tell that they are lying, some are bad liars and you might be able to tell, and some are terrible liars and no check is needed. There are auto-fails, auto-successes, and a few edge cases. For the most part, I lean towards auto-fail. I assume that all my npc's are competent and try their best to lie. If the players want to find out if they are lying, they have to catch the npc's on falsehoods or inconsistencies in their story, rather than a lucky dice roll. To me that is far more exciting roleplaying wise.

While autofailure is, in the abstract, always one possibility, personally I don't think it makes a very good default independent of circumstances. Can you give any additional insight (haha) as to why you do this?

Nice one. I do this because I want my players to actually pay attention to what an npc is saying. I want them to remember what they know about the story and use that to determine lies and falsehoods. When a person lies, just like in real life, you usually can't tell. But what a player can do, is pay attention to what an npc says, and to subtle cues that are given while he says it.

When a player searches a room, I ask them what they are looking for. If they want to disable a trap, I ask them how they want to disable it. I do the same with social checks. You can't just tell a person is lying, but perhaps you can tell if he's nervous? Or whether the things he says are factual? The player needs to state an approach, and then I determine if it's an auto-fail, auto-success or a dice roll.

Ok, I assume this is somewhat lighthearted and you really mean that you think he would be caught (regardless of what you might want), otherwise it certainly sounds a bit railroad-ish.

Some npc's are just terrible liars, or the thing they are trying to lie about is so painfully obvious, that the players would be fools to believe it.

Is your procedure in this case to rule an autosuccess or is this the case that you mentioned above in which the NPC would exhibit a 'remarkable behavior'?

I would have the npc show a remarkable behavior, or act him out in a way that makes it painfully obvious that he's lying. I'd have the npc misspeak for example, and almost blurt out something he didn't mean to say. Or perhaps the npc simply cracks under enough pressure by the players, and confesses to lying. Either way it's an auto-success.

I don't understand the distinction between being able to tell if the one NPC is "telling the truth" and being able to tell whether other NPCs are "on his side". To me, these both seem to be instances of being able to discern something about an NPC's mental state. What is it that causes you to treat them differently?

In my opinion, you can't read lies, but you can read emotions, gestures, looks. How those clues are interpreted is up to the players. I always expect my players to state an approach to what they are trying to achieve, and then I decide if the outcome is in doubt.

So when an npc says he has the players surrounded, I don't want my players to say "Can I make an insight check to tell if he's lying?". Instead I want them to say something like "Does it look like he has a lot of allies in the bar?" or "Do I see other people with weapons?" or "Does the npc seem nervous?" or "How does the rest of the tavern respond to these threats?"

Depending on the stated approach, the players may have to make an insight check, but it might as well be a perception check, or no check at all.

 

[GothicEmperor]

If I have a Deception stat, I use the passive deception. Else, the normal procedure of selecting DCs.
I don't stat out most NPCs, so mostly the latter.