Man, I am terrible at compiling lists of GM Resolutions, I left off my renewed effort at NPC voices and came to realize today that I also left off my Insight/Detect Lie resolution. To whit, I am done allowing Insight/Sense motive checks to tell when an NPC is lying...
Now, this has been a pet peeve of mine for quite a while, but this year I'm putting my foot down and no longer allow players to declare "Is [NPC] telling the truth? I'm rolling Insight". But, but Zack! You cry, the D&D 5e Player's Manual allows it... and, sure I guess you could read it like that... here it is... the description of the Insight skill (which replaced earlier editions equally terrible "Sense Motive")...
Insight. Your Wisdom (Insight) check decides whether you can determine the true intentions of a creature, such as when searching out a lie or predicting someone’s next move. Doing so involves gleaning clues from body language, speech habits, and changes in mannerisms.It's right there "true intentions of a creature... searching out a lie..." to which I say, hooey... HOOEY! Continue reading or skip right to the TL;DR
Here's my problem with Insight. Players don't use it when 'searching out a lie' they bald-faced declare "is that a lie? I roll Insight". They don't say "I'm watching how the goblin moves when talking to us" they say "is the goblin lying?". But that's not even it... my impression, from mostly being a GM, is that players don't even want to know if the NPC thinks they're telling the truth but the TRUTH, the meta-game truth as they would perceive it as a player, not as the NPC or even their PC perceives it.
What do I mean? Say the PCs capture a goblin after a long and bloody (or even short and bloody) fight. Said PCs have heard that beyond the goblin caves there is a dragon with a great treasure hoard. They spare this goblin's life (after brutally murdering his friends and family) and then demand that he tell him if there is a dragon in the caves below... Now, never-mind that perhaps this goblin, already brutalized and traumatized at the hands of the PCs might not talk, if he does, there's a good chance that a player will throw down a d20 and say "Insight, is that dirty lying goblin telling the truth?" What's a GM supposed to do with that? Say the goblin said "Yes" and the GM says, you know he's lying. Now the players might not go down further to fight the wyvern below... Or the PCs do go down and find the wyvern and are mad but the GM just says "uh, obviously you only asked about dragons, not wyverns..."
Players when the ask if an NPC is lying see to be seeking the TRUTH the way a video game player might find the truth by consulting a walk-through document, that is, the want to know the exact programming, that if they go into the goblin caves now there will not be a dragon, but if they take a long rest there will be because the dragon will have returned. Or, they want to know the truth as printed in the adventure module, that the dragon has 330 HP and can use its fire-breath twice.
But, in a way, that's all beside the point because do the PCs gain anything from knowing if that random goblin NPC is telling the truth about whether a dragon is below? Probably not. They are probably going to act in the same manner they would have if they hadn't interrogated a random goblin NPC. Absent that random goblin, the players are probably going to make their decision based on resources (HP, rests, time, etc) and it doesn't matter much if that goblin lies and says there's a dragon down below in the hopes that the PCs will go away instead of heading down and probably murdering the remainder of his tribe.
Also, go back and read that Insight description... "gleaning clues from body language, speech habits, and changes in mannerisms"... Now, think about PCs interrogating random goblin NPC after blasting away his friends with fireballs and vorpal swords. Is his body language going to be anything but nervous? He probably doesn't speak Common as a first language and it's likely that none of the PCs speaks Goblin as a first language either, so would they really be able to expertly deduce from his speech habits how truthful he was being? Finally, changes in mannerism? They just met this poor goblin, who is assuredly in shock, are changes in his mannerisms really going to be the clues our canny PCs can use to decipher his truthiness?
But, fucking Insight is printed right on that damned character sheet and the PC has a +7 to it, so they're going to hoist up their favorite d20 and declare "Is the goblin lying? I roll Insight"...
And from now on, I'm going to be the Asshole GM who says, "No, no you do not." Let's look to some other systems for better answers...
While trying and mostly failing to be subtle about it, their selfappointed spokesman here, the thoroughly drunk but wily swashbuckler Clendennon, tries to learn how they got here.
Consult the Ancient
When you Speak Wisdom, you may choose not to roll and instead listen to the giant’s soul. The GM will tell you two true things and one lie, based on the giant’s understanding and motives.
You cannot use Discern Realities or Speak Wisdom to learn which statements are true. You must decide for yourself.