How can a character detect lies?

Question

In a campaign using both Advanced Dungeons & Dragons and Advanced Dungeons & Dragons, 2nd Edition material, what methods are available to detect lies or sense deception, like seeing through a disguise?

The scenario was with a traveling Hag disguised as a Gypsy who was lying to the Adventuring party trying to convince them to deliver an amulet (cursed of course) to her "niece".

There's a "Penetrate Disguise" spell, which would detect the Hag's Gypsy/Merchant occupation was false (as the Hag was strictly speaking a "witch", not a "merchant"), but would not detect she was shape shifted into an old woman. Detecting she's not really a gypsy merchant indirectly notifies the party she's deceiving them, even if her words sound authentic.

There's "Detect Evil" available to both 1st level clerics and Paladins (which is how the party solved the problem) though this doesn't detect lies, it does present a reason for the group to be more distrusting.

"Detect Lie" was a 4th level spell (7th level caster), and being a 4th level party, there was no way they were going to have access to that.

and the spell-like ability to change self at will. Hags use this last ability to attract victims, frequently posing as young human or demihuman females, helpless old women, or occasionally as orcs or hobgoblins. A disguised hag reveals her true form and leaps to the attack when weak opponents come near. Against well armed and armored parties, hags maintain their disguise and employ further trickery designed to place the intended victim in a more vulnerable position. This trickery can take any of several forms, including verbal persuasion, leading the victim into a prearranged trap, and so on. (MM 181)

I gave some other subtle hints (introduced herself as Meghan Greenespire, Meg is the name of the Green Hag from Legend, called her niece Lizabelle, the "Liz" pronounced "LIES")

So im wondering if something like Sage Knowledge: Folklore (witches & hags), or the priest proficiency Observation (both from Spells & Magic) can be blind checked - i.e., non proficient checks for people who don't have those proficiencies, and perhaps what kinds of penalties? I ask because in AD&D some proficiencies allow a check with a penalty, and others don't allow any check at all. Seems like Folklore knowledge would be completely random, while Observation or similar proficiencies would be a check at a penalty.

Answer 1

There were a few spells or abilities that tended to ruin plots without some DM fudging, and fit the bill of what you are looking for:

Detect Lie (reversible)

(Divination) Reversible

Level: 3

Explanation/Description: When the cleric employs this spell, the recipient is immediately able to determine if truth is being spoken. The spell lasts one round for each level of experience of the cleric casting the detect lie. Gold dust is necessary for this spell. Its reverse, undetectable lie, makes bald-face untruths seem reasonable, or simply counters the detect lie spell powers. The reverse spell requires brass dust as its material component.

Zone of Truth

Level: Cleric 2

Creatures within the emanation area (or those who enter it) can’t speak any deliberate and intentional lies. Each potentially affected creature is allowed a save to avoid the effects when the spell is cast or when the creature first enters the area of effect.

Affected creatures are aware of this enchantment. Therefore, they may avoid answering questions to which they would normally respond with a lie, or they may be evasive as long as they remain within the boundaries of the truth.

ESP

(Divination)

Level: 2

Explanation/Description: When an ESP spell is used, the caster is able to detect the surface thoughts of any creatures in range - except creatures with no mind (as we know it), such as all of the undead. The ESP is stopped by 2 or more feet of rock, 2 or more inches of any metal other than lead, or a thin sheet of lead foil. The magic-user employing the spell is able to probe the surface thoughts of 1 creature per turn, getting simple instinctual thoughts from lower order creatures. Probes can continue on the same creature from round to round. The caster can use the spell to help determine if some creature lurks behind a door, for example, but the ESP will not always reveal what sort of creature it is. The material component of this spell is a copper piece.

Apart from that, a rule made official in the early 1980's allowed DM's to essentially create their own ability checks for things like this:

The DM may want to base a character’s chance of doing something on his or her ability scores (Strength, Dexterity, and so forth). To perform a difficult task (such as climbing a rope or thinking of a forgotten clue), the player should roll the ability score or less on 1d20. The DM may give a bonus or penalty to the roll depending on the difficulty of the action.

Answer 2

Aside from the magic-user spells Detect Lie and ESP and the Cleric spell Zone of Truth, already mentioned in other answers, there are a few other strategies to determine if an NPC is lying.

In 2e there is also a 4th level Priest spell Detect Lie.

In the 2e Tome of Magic there is a 2nd level Priest spell called Mind Read that can be used to determine an NPC's thoughts and can tell what an NPC is, similar to the Magic-User ESP spell.

To detect whether someone has put on a disguise or is pretending to be something they are not, the 3rd level Priest spell Memory Read (Tome of Magic) could be helpful.

The 1st level Priest spell Emotion Read (Tome of Magic) can also be used to get a read on an NPC's emotions.

A priest might also try a Divination (4th level Priest spell, Player's Handbook).

The fifth level Priest spell True Seeing (Player's Handbook) should also be able to see through a disguise.

A roundabout way of doing it might be to cast Charm Person or Mammal (2nd level Priest, Player's Handbook) and then just ask politely. The 4th level Priest spell Mental Domination (Tome of Magic) could also work for this.

It would be overkill, but let's not forget to mention Wish and Limited Wish, both of which can easily see through a disguise.

A good way of going about it is for a Priest to cast Emotion Read, Mind Read, and Detect Lie in three successive rounds. Emotion Read has "instantaneous" duration, so it's just a flash of the NPC's feelings. Mind Read and Detect Lie both have a duration of one round per spellcaster's level, so you should be able to have them going at the same time.

Answer 3

The second-level Magic-User spell ESP can do it, and only requires a third level caster. The AD&D 1e description reads:

Explanation/Description: When an ESP spell is used, the caster is able to detect the surface thoughts of any creatures in range — except creatures with no mind (as we know it), such as all of the undead. The ESP is stopped by 2 or more feet of rock, 2 or more inches of any metal other than lead, or a thin sheet of lead foil. The magic-user employing the spell is able to probe the surface thoughts of 1 creature per turn, getting simple instinctual thoughts from lower order creatures. Probes can continue on the same creature from round to round. The caster can use the spell to help determine if some creature lurks behind a door, for example, but the ESP will not always reveal what sort of creature it is. The material component of this spell is a copper piece.

Using it for detecting lies naturally requires having enough suspicion to cast it. It's also very helpful to have someone who can converse with the target about who they are, what they're doing and so on, so that you can observe the difference between their thoughts and their statements. Of course, this may make the target suspicious they've been spotted. The 2e version has additional material about using it in interrogations, demonstrating that this is a valid tactic.