Silent Legions question...how to determine if an in-game character is lying? Call of Cthulhu uses the Psychology skill to spot untruths. Delta Green uses HumInt (Human Intelligence) skill. In Silent Legions, would it be the Perception skill to notice subtle clues that a character my be engaged in deception, or would it be a Mental Effect Saving Throw to avoid 'falling' for the lie?
This seems like a Persuade v [one of Persuade|Perception|Culture] opposed skill check, to me.
You decide whether or not what the person is saying to you is plausible.
There's no skill use that reliably lets you tell if somebody's lying to you; if you gave that ability to a simple skill check it'd be easy to optimize and turn your PC into a walking lie-detector. In a mystery game like Silent Legions, that's not generally going to be what you want. If the PCs think an NPC is snookering them, they should go investigate what the NPC said and follow it up to see whether or not the story holds together.
What about reversing the question and having someone be able to Lie Convincingly? The higher the stakes the greater the difficulty. It won't tell you the truth, only that someone is actually nervous about something. In other words instead of having expert interrogators you have incompetent liars.
In particular the abilities of amateurs versus professionals (spies, con artists, and on the other side police detectives, customs inspectors, trained interrogators, and mothers).
i would expect that to lie convincingly (i.e. persuade them that what you're saying is true is either "does it sound reasonable to the ref" or is a use of Persuade skill).
Hello all - thank you for addressing the question. I think, at my table, I might make the situation an 'opposed skill roll.' Have the deceiver roll 2d6 and add level of Persuade skill (if any), versus the target rolling 2d6 and adding Perception skill ranks (if any). The Perception skill here would be for the target to notice the deceiver acting nervous, sweating a bit, shifting their gaze, etc. all the telltale signs of someone not being forthright. A simpler way would be for the target (if a player character) to roll Perception versus a Difficulty Number set by the GM, representing the proficiency with which the deceiver tells untruths. And of course, as Mr. Crawford states, any falsehoods can be sources of investigation and due diligence for those who suspect lies are being told.
all of those signs of lying are also signs of dozens of other emotions/physical/mental states. Reading body language in order to determine truth is only as good as flipping a coin unless you know your subject intimately. This holds true for both veteran interrogators and random people. Maybe the npc is sweating heavily and shifting his gaze around because five heavily armed strangers wandered into his place of business and started interrogating him.
Still, it’s a genre trope, so it’s appropriate if you want to use it.