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

S'mon · Mar 23, 2019

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

Giltonio_Santos · Mar 23, 2019

I believe that should be a persuasion roll for the NPC, with a base DC of 10. You can decrease the DC to something as low as an automatic success (DC 0) if characters are in friendly terms, or increase it up to a DC of 20 if the interaction happens under an atmosphere of strong hostility.

EDIT: I would also apply the PC's insight skill as a negative modifier to the persuasion roll. Insightfulness should make you more adept at detecting sincerity.

GlassJaw · Mar 23, 2019

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.

GlassJaw · Mar 23, 2019

Giltonio_Santos said:
I believe that should be a persuasion roll for the NPC, with a base DC of 10. You can decrease the DC to something as low as an automatic success (DC 0) if characters are in friendly terms, or increase it up to a DC of 20 if the interaction happens under an atmosphere of strong hostility.

EDIT: I would also apply the PC's insight skill as a negative modifier to the persuasion roll. Insightfulness should make you more adept at detecting sincerity.

The only time I roll a social skill for an NPC opposed by a PC is Deception. A player is always the final arbiter as to whether their character is persuaded or intimidated.

iserith · Mar 23, 2019

I likely don't set a DC. The character succeeds, no roll, perhaps because the truthful NPC exhibits no body language, speech habit, or change in mannerisms that suggest a deception.

Guest 6801328 · Mar 23, 2019

This is yet another reason why using a skill to "detect" truth or lies is a terrible idea.

Charlaquin · Mar 23, 2019

iserith said:
I likely don't set a DC. The character succeeds, no roll, perhaps because the truthful NPC exhibits no body language, speech habit, or change in mannerisms that suggest a deception.

This. If an NPC is telling the truth, they exhibit no signs that they are lying, therefore there is no uncertainty if a PC attempts to discern whether or not they are lying by observing their behavior.

Elfcrusher said:
This is yet another reason why using a skill to "detect" truth or lies is a terrible idea.

And this. When an NPC lies to a PC, I roll for the NPC against the PC’s passive Wisdom (Insight). On a failure, I tell the PCs what they notice - for instance, that the NPC is having difficulty maintaining eye contact and their brow has a faint glimmer of sweat or something. On a success, I let the NPC’s statement stand on its own. In either case, it is up to the player whether their character believes they are being lied to or not.

jgsugden · Mar 23, 2019

This is the way I do it:

When a PC attempts to use a skill without spending an action, they generally do so "passively", meaning they add 10 to their skill and use that as the result (with a +/- 5 for advantage/disadvantage). If they take an action to perform the skill, they get to roll a d20, but their "passive" score is a floor for their result unless there is time pressure or other challenges that make things difficult.

When a player wishes to sound convince someone they are being honest, they may roll deception or persuasion rolls. For persuasion, sounding sincere when telling the truth is DC 15 or the observers passive insight, whichever is lower. For deception, the DC is the observer's passive insight.

TaranTheWanderer · Mar 23, 2019

Insight is great for noticing if an ally is charmed and acting strangely. If you know the person, you get advantage on your passive check or roll.

Regarding the OP:
If a PC is unsure whether an NPC is being honest but that NPC is actually being honest, I roll the dice behind the dm screen and then Tell the player the truth that NPC seems to be sincere. I don’t even bother looking at the dice roll. I like adding that little bit of uncertainty. The fact that they are asking for a roll shows they are suspicious. Either the player will learn to trust the NPC (because of in game actions)or they won’t but I won’t just tell him, “oh yeah, he’s totally trustworthy.”

Charlaquin · Mar 23, 2019

TaranTheWanderer said:
If a PC is unsure whether an NPC is being honest but that NPC is actually being honest, I roll the dice behind the dm screen and then Tell the player the truth that NPC seems to be sincere. I don’t even bother looking at the dice roll. I like adding that little bit of uncertainty.

Query: It would seem to me that not looking at the die before announcing the result would remove the uncertainty that you roll the die in order to add; is this a bug or a feature of your approach?