I HAVE HAD A THOUGHT!

Okay, there’s an old bind that GMs can run into when players are interacting with NPCs: the GM wants the NPC to mislead or outright lie to the players, but the very mechanics of such an action automatically tip your hand.

If you tell the players to roll an Insight/Intuition/Detect Lie check, they know they’re being bluffed. Very talented players will be able to keep that meta-knowledge separate from their character’s action, but most players can’t help but take up a defensive posture during the conversation with the lying NPC.

If you don’t tell the players and rely on them to call for their own lie detector checks, they’re either going to get paranoid and roll checks all but constantly or you’ll have to drop huge hints that an NPC is lying.

I come to you, dear friends and readers, with a solution! As an added bonus, it works for persuasion or other social skill checks as well! If you plan to have the NPC lie or attempt to persuade the characters, roll the check and base how good the lie is on how well they roll. Don’t call for any corresponding checks from your players; just add more faulty details or tells if the NPC rolls poorly or make it airtight if they score high. If the players pick up on the suspicious bits, they will then know to call for a lie detection check.

Obviously, this places an extra burden on the GM: you will have to know how to make a lie more or less convincing. This will be one part practice and one part research! Learning to make a lie more effective is substantially easier, so here are a few links to help in that regard: 1 2 3.

Now, making a lie bad is easy. As a bonus, it’s fun and will entertain your group. Remember the last time someone tried to pull a fast one on you but you knew they were lying? They put quite a performance, didn’t they? Here are a few tells to sprinkle in when an NPC botches their bluff check:

Nervous fidgets - Tap your foot, get up and pace, gesture unnecessarily, scratch the back of your neck, and/or lean back and away from your players.
Lack of eye contact - For the duration of the lie, make sure you avoid looking any players in the eye. Look away at some detail in the ceiling or catch someone’s eye and then immediately look down at your papers for a few seconds.
Hesitation - Add lots of umms and uhhs into the NPC’s speech, have them pause before answering questions.
Unnecessary Details - the more complex a lie is, the more likely it will lose consistency: go into laborious detail. The bruises on the warden’s prisoners weren’t from a beating, no! They must have tripped over their chamberpots and banged their heads against the bars a few times on the way to the floor!
Defensive Posturing - People that lie often become agitated when cornered. NPCs could lash out at being questioned, with arms crossed  and a scowl on their face. How dare the player characters ask why the warden’s breath smells of whisky! He’d never drink on the job!
Facial Touching - When under stress, people tend to touch their face by reflex. Scratch at your nose, wipe your forehead, or push your hair behind your ears.

Now, if you’ll excuse me, I’m going to go test this as soon as possible. If anyone gives it a try or has feedback, let me know!