Lie Detection

[ironphoenix.livejournal.com]

As we discussed, here's my idea for a magical lie detector power:

Detect Lie, Hearing Sense Group, (5 AP), Sense (+2 AP), +7 PER for Detect Lie (+7 AP): Base Total 14 AP
Invisible Power Effects (all except Detect Magic): +3/4 Total: 24 AP
Requires a Skill Roll (sense magic skill) to activate (-1/2) at no AP penalty (cancels -1/2) AND requires PER roll (-1/4) contested against speaker's Acting (-1/4)
Side effect (15 AP) only on critical failure of magic skill roll (-0)
Real cost is 24 AP /1.5 = 16 RP
Fixed slot cost is 16 RP/10 = 2 CP

This gives Sean an effective PER of 21 for the skill vs skill contest, with Sean winning ties. For people whose Acting skill (adjusting for bonuses/penalties) is 11 or less, Sean's probability of detecting a lie is better than 99%. At skill 14, they have a 5% chance of Sean not catching them; at 18, it's about 20%; at 21 (even skill levels), it's about 46%. To have an 80% chance of lying successfully to Sean, a person would need an effective Acting skill of 25.

As I envision it, this spell makes any statement the speaker believes to be false obvious to Sean. Statements which are presented with more certainty than the speaker actually has, partial lies, and statements which are not believed to be true without qualifiers which are being intentionally withheld, would trigger this Detect. This becomes subtle, and bonuses or penalties may be appropriate, depending on the magnitude of the deviation from the truth.

This is a tricky business... the examples below (or an upper-year course in logic and rhetoric) may be helpful in understanding the subtleties.

The 99 bus route operates Monday through Saturday. Here is a list of circumstances and the status of the Detect:

Suppose you say that you're going to Bayshore, and ask a person when the 99 will arrive at the corner of Bank and Catherine...

...on Wednesday at 2:15, and he says that the 99 is scheduled to arrive at 2:30 p.m., except on Sundays and Holidays. No lie detected. (This is the exact truth.)

...on Wednesday at 2:15, and he says that the 99 will arrive at 2:30. No lie detected. (This omits some information which is not believed by the speaker to be necessary to answer the intent of the question.)

...on Sunday at 2:15, and he says that the 99 will arrive at 2:30, knowing that it doesn't run on Sunday. Lie by omission detected. (It will arrive at 2:30 the next day, but this is not the next 99 to arrive there, since there will be several before it. This would only be said by someone with malicious intent.)

...on Sunday at 2:15, and he says that the 99 will arrive at 2:30, believing that it runs every day. No lie detected. (This is an honest error.)

...on Sunday at 2:15, and he says that you can cath the 99 to Bayshore there, knowing that it doesn't run on Sunday. No lie detected. (This is a lie by evasion.)

...on Sunday at 2:15, and he says that the 99 will arrive at 2:30, knowing that he is unsure which days it runs on (because, for example, he understands that the striped number indicates that the schedule or route varies by day or time.) Lie detected. (This is a lie by pretense of certainty.)

...on Saturday at 2:15, and he says that the 99 will arrive at 2:30, knowing that he is unsure which days it runs on (because, for example, he understands that the striped number indicates that the schedule or route varies by day or time.) Lie detected. (This is also a lie by pretense of certainty, even though the statement itself is true.)

Comments

[m-danson.livejournal.com]

So what you are saying is that this detects the physical tip-offs that a person is lying, much like a polygraph. Correct?

So three possible breakdown points would be:

1) when a person has no physical tip-offs when lying (ie he is a psychopath or otherwise capable of strict self-control... giving false negatives),

2) when a person is aggitated enough to over-write his normal lying tip-offs (ie someone who has been seriously threatened by a third party might be aggitated enough to give false positives), and

3) when used against a race that has very different tip-offs (ie how the hell can you tell if a gremlin is lying??).

On normal people and in normal circumstances it will function practically perfectly as a lie detector. In 'adventuring' situations it works most of the time against most people. In extreme situations (ie trying to interrogate Silver or Jack) it will give you a guess but its reliablity is questionable.

Is this how you see it?

[ironphoenix.livejournal.com]

An insane individual's reality is a strange and wondrous thing... I believe that Sean would detect them saying something other than the truth as they experience it.

Someone agitated (e.g., under the influence of mind control or a successful presence attack) would probably be identifiable as an unreliable subject, because everything would cause nervous responses. This would probably act as an effective modifier to their Acting roll, where instead of suppressing positives, they effectively boost their negatives so that the difference is much smaller (and hence harder to detect.) A rule of thumb might be a modifier of 1 for every 2 points the presence attack or mind control succeeded by (they're very similar in effect). Naturally, the person can be calmed down and the questions asked again under more favorable circumstances, though!

Again, this would be a modifier, I think. It would depend on familiarity and experience with that particular race or similar races.

Some modes of communication make this power unusable (e.g. Jasper's mind link) because no hearing is involved.

On normal people and in normal circumstances it will function practically perfectly as a lie detector. In 'adventuring' situations it works most of the time against most people. In extreme situations (ie trying to interrogate Silver or Jack) it will give you a guess but its reliablity is questionable.

Pretty much. Silver and Jack are particularly tough because of the combination of possible delusions combined with very high effective acting skills. Even if Sean can tell whether or not they're lying (far from certain), he's still not sure what the truth is. His M.O. would probably be to use a presence attack boosted by glamour (see the upcoming issue of Sean's Spiffy Spellbook for details) to encourage them to tell the truth (to try to apply a negative modifier to their mad acting skillz) and interrogate them afterwards.

Magic makes everything better... it's like ninjas!