Detect Lies
This house rule allows users of Detect Lies to make their own rolls, which some players enjoy. This house rule also includes information on using lie detection equipment. If you consider Detect Lies to be a cinematic skill, this house rule renders it less so. (If you like this house rule, you might also be interested in my Interrogation house rule.)
Per/Hard
Defaults: Perception-6, Body Language-4, or Psychology-4
This is the ability to determine if somebody is lying by observing and interpreting physiological changes and psychological mannerisms.
Detect Lies vs Acting
A successful Detect Lies roll means you noticed a tell that indicates the person either lied or told the truth. The potential liar, however, gets a chance to defend using Acting (but not Fast-Talk). If the liar makes his roll by more than you made your Detect Lies roll, the GM will give you an answer that favors the liar--you misinterpret a tell or believe a false one. An unsuccessful Detect Lies roll means you do not pick up any tells or they’re inconsistent. A critical failure means that person is particularly hard for you to read for some reason and you don’t trust yourself to reliably interpret their tells for the rest of that encounter. A critical success on your part or a critical failure on their part indicates the revelation of additional and/or unexpected information. Because of this game mechanic, PCs can be allowed to make their own Detect Lies rolls. WARNING: Under this house rule, a career liar will often fool you.
| Acting Roll Succeeds By More | Acting Roll Succeeds By Less or Fails | |
|---|---|---|
| Detect Lies Roll Succeeds | You incorrectly interpret a tell | You correctly interpret a tell |
| Detect Lies Roll Fails | You don't pick up any reliable tells | You don't pick up any reliable tells |
An attempt to Detect Lies accurately requires you to get a feel for the tells of a particular individual; this takes about 30 minutes for a total stranger. For a first-time subject that you've just met, you start with a -5 penalty. Lessen this penalty by 1 for every 5 minutes of quality time you spend with the subject. This means that, if possible, you should spend about a half hour conversing with a stranger before you use Detect Lies.
If the liar has time to prepare his story--at least 30 minutes to "get his story straight"--he may get up to a +5 bonus.
Electronic Operations (Medical) vs Body Control
Detecting lies with lie detection equipment requires having the Electronic Operations (Medical) skill. Lie detection equipment becomes available at TL 6 and gives a bonus to Detect Lies skill equal to your margin of success with Electronic Operations (Medical) skill, up to a maximum of TL/2. The person lying can resist with Body Control by regulating the normally involuntary physiological changes that occur when they lie. This is a regular contest, Electronics Operations (Medical) vs. Body Control. (Option: a good Actor without Body Control skill may be able to get into character enough that they, for all intents and purposes, adopt a new personality that is consistent with their lie. This is difficult and amounts to a -5 penalty to their Acting skill if they've had time to prepare (30 minutes minimum); if they haven't had time to prepare, the penalty is -10.)
| Body Control Roll Succeeds By More | Body Control Roll Succeeds By Less | Body Control Roll Fails | |
|---|---|---|---|
| Electronic Operation (Medical) Roll Succeeds | You gain no bonus | You gain a bonus equal to your margin of success less their margin of success up to a maximum of TL/2 | You gain a bonus equal to your margin of success up to a maximum of TL/2 |
| Electronic Operation (Medical) Roll Fails | You gain no bonus | You gain no bonus | You gain no bonus |
When using lie detection equipment, you may make one Detect Lies vs. liar roll for the entire session if you wish. I.e. you ask all your questions then go over the results of the polygraph later. If you are working alone, this is the preferred method, as questioning while trying to actively interpret the lie detection equipments output would result in a -1 multitasking penalty to either your Detect Lies or Electronic Operation (Medical) skill.
Modifiers
+1 for Sensitive or +3 for Empathy (p. B51), or -3 for Low Empathy (p. B142); +4 if your subject is Easy to Read (p. B134). If the subject is of a different species, the GM may assess a penalty - see Physiology Modifiers (p. B181). Up to a TL/2 bonus with lie detection equipment. Up to a -5 penalty due to reduced time. Taking extra time [B346] can give a bonus. The liar may also receive bonuses; up to a +5 bonus if they've prepared for 30 minutes or more. (This means non-Actors that have time to prepare roll against their IQ.)
Example 1: With Lie Detection Equipment
You have Detect Lies at 15 and Electronic Operation/TL9 (Medical) at 12; the con man has Acting 17 and has had ample time to prepare his story. Your Electronic Operation/TL9 (Medical) roll is a 9 (made by 3) and the con man’s Acting-5 roll is a 13 (missed by 1); you win the contest and the lie detection equipment gives you a bonus of +3 (your margin of success). After spending half an hour with the grifter hooked up to lie detection equipment, you roll against your Detect Lies+3. If you fail, your lie detection efforts are inconclusive; if you succeed, the con man (we’ll assume he lies) gets an Acting+5 roll. If he succeeds by more than you, then he appeared to be telling the truth; otherwise, he appeared to be lying. You get a +3 because of the lie detection equipment; he gets a +5 because he had time to craft his story. It would be appropriate to make the quality and quantity of lies caught dependent on your margin of successful in the contest.
Example 2: Without Lie Detection Equipment
At TL5 you ask a working women in a saloon her age and want to know if she’s telling you the truth. You have Detect Lies skill at 12; she does not have Acting skill. This is a contest of your Detect Lies-5 vs her IQ-5. You take full reduced-time penalties in a situation like this. After about of half hour of conversation and observation, you could ask again (at a -2 penalty this time, for a repeated attempt). Indeed, it is difficult to know with certainty when you are being lied to by a stranger in a social situation.
See Also
2d Damage optional | Combat Maneuvers | Interrogation | Meditation | Tactics