How to run a Mystery is D&D

[Chained Birds]

So I plan to one day run a mystery-type game where the PCs would play as detectives trying to solve various cases, from murders to unexplained phenomena. The trouble I'm having is creating these mysteries or at least determining the challenge of a particular mystery vs the capabilities of the PCs / actual players.

As in, what level can a PC be in a 3.P game for a Murder case to be resolved by just "magicing" or "psionicing" an answer? How many evasive tactics do I need to employ before it just becomes too much? Is a challenging mystery one where the players pretty much give up and start asking for hints to point them where they should be? What is the best level to do this sort of game, or can any level work?

I have several more questions, but for now I'd at least like to here some people's experiences on running mysteries in D&D so I can have an idea of what to expect or work on for the game.

Any input would be greatly appreciated!

[SimonMoon6]

How to ruin a mystery:

(1) The 5th level cleric spell Commune. "Is he the killer? No, how about him? How about him? Oh, okay, he did it!"

(2) The 3rd level cleric spell Speak with Dead can be a mystery killer too, though it's possible to set things up so the corpse doesn't know who killed him. Typically, though, it'll be a "Yeah, Bob killed me in the conservatory with the candlestick" sort of situation.

(3) The 5th level wizard spell "Contact Other Plane" is similar to Commune.

So, you don't want to have 9th level characters trying to solve a mystery because all they'll do is cast one spell. Of course, you also have to deal with the whole, "I go buy a scroll of Commune" problem too...

But, on the other hand, if the mystery gets too hard and the PCs need hints, well, that's usually when the bad guy decides the detectives are getting too close to the truth, so he sends some hired thugs out to kill them, who the detectives can then interrogate.

[jywu98]

Generally, a mystery campaign needs to be low-magic. You should also remove skills such as Intimidate, Gather Information, etc. and resolve those through roleplaying.

[Rhynn]

(2) The 3rd level cleric spell Speak with Dead can be a mystery killer too, though it's possible to set things up so the corpse doesn't know who killed him. Typically, though, it'll be a "Yeah, Bob killed me in the conservatory with the candlestick" sort of situation.

The very existence of the spell speak with dead would affect how murders are committed.

In Artesia: Adventures in the Known World, the entire world has adapted to the common knowledge that the spirits of the dead can answer questions (and could, theoretically, give witness); it's common knowledge because once a year, the spirits of your dead ancestors get to visit you and your family... So, every murderer will wear a hood or mask that conceals their identity, and otherwise endeavor to make certain that their killer cannot recognize them. It also matters because even if you're never caught, unless you used horrible and powerful curses to doom your victim's spirit to be lost in Limbo and devoured there, even if you get away with your crime, your victim will be waiting for you when you eventually die and go to Judgment, and a single murder on your record is enough to send you to Hell.

Commune is trickier, but the wording of it does contain some subtleties.

3.5 / PF commune: "You contact your deity—or agents thereof —and ask questions that can be answered by a simple yes or no. [...] The answers given are correct within the limits of the entity’s knowledge. “Unclear” is a legitimate answer, because powerful beings of the Outer Planes are not necessarily omniscient. In cases where a one-word answer would be misleading or contrary to the deity’s interests, a short phrase (five words or less) may be given as an answer instead."

How exactly commune works or doesn't will say a lot about the theology and cosmology of your setting. A specific subtlety applied there might suggest great and interesting specifics about deities and their servants, attitudes, and activities. (Reducing the power of a single over-powered adventure-shortcutting spell is hardly poor DMing, either.)

[Grod_The_Giant]

The single most important prerequisite is that your players have to want to play a mystery game. If they don't, they'll break out all the cheaty-magic stops and/or sit there and stare at you until you give them answers.

The second consideration to look at what your players can, potentially, do. If someone can cast speak with dead, they probably will-- so plan for that, and have a cryptic clue ready. If someone has maxed out Gather Information, work out the kind of things they can learn from it. Design the mystery around your players' abilities, rather than cutting their abilities around to fit the mystery.

[Karnith]

The very existence of the spell speak with dead would affect how murders are committed.

In Artesia: Adventures in the Known World, the entire world has adapted to the common knowledge that the spirits of the dead can answer questions (and could, theoretically, give witness); it's common knowledge because once a year, the spirits of your dead ancestors get to visit you and your family... So, every murderer will wear a hood or mask that conceals their identity, and otherwise endeavor to make certain that their killer cannot recognize them. It also matters because even if you're never caught, unless you used horrible and powerful curses to doom your victim's spirit to be lost in Limbo and devoured there, even if you get away with your crime, your victim will be waiting for you when you eventually die and go to Judgment, and a single murder on your record is enough to send you to Hell.

Alternately, the murderer could take the body with him or otherwise destroy it, as Speak with Dead requires the corpse of the dead person. The murderer could even just disfigure the victim's mouth, as the spell specifies that the body "must at least have a mouth in order to speak at all."

Also remember that once the players have a suspect, it will be child's play to verify whether that person committed the crime using spells. Things like Charm Person, Detect Thoughts, Zone of Truth, and so on will make hiding things from the players difficult.

Amusingly, some aspects of a mystery work pretty well at mid- to high-levels, as the culprit, assuming that he is a caster, will be able to use his own magic to hide the evidence of his crime. Things like Polymorph Any Object (to hide the body or any evidence), Programmed Amnesia/Mindrape, Trap the Soul, Mind Blank, Screen, Sequester, and so on make challenging cases, though it is difficult for anyone but devoted spellcasters to solve them.

[Rhynn]

The murderer could even just disfigure the victim's mouth, as the spell specifies that the body "must at least have a mouth in order to speak at all."

Oh, good point. That's almost trivially easy, then - remove the jawbone and take it with you. Uh... well, okay, not trivial, and pretty gruesome, but definitely doable.


Also remember that once the players have a suspect, it will be child's play to verify whether that person committed the crime using spells. Things like Charm Person, Detect Thoughts, Zone of Truth, and so on will make hiding things from the players difficult.

This one's easier: sometimes, figuring out who did it isn't enough. The PCs may lack the power to do anything about it themselves, and a spell-caster going "I swear, I detected he was lying!" isn't probably too persuasive (and a confession isn't persuasive precisely because if charm person and similar spells). Getting hard evidence may be necessary, and that may still require a lot of thinking and legwork.

Incidentally, 9th level clerics ruin mysteries involving murders anyway: raise dead. 13th and 17th levels ruin it completely, unless equally powerful magic is involved (resurrection and true resurrection).

[Agincourt]

The Alexandrian blog has some good tips for running a mystery. If you follow this links to other posts, you'll get some really good advice:

http://thealexandrian.net/wordpress/1118/roleplaying-games/three-clue-rule

[Pickford]

So I plan to one day run a mystery-type game where the PCs would play as detectives trying to solve various cases, from murders to unexplained phenomena. The trouble I'm having is creating these mysteries or at least determining the challenge of a particular mystery vs the capabilities of the PCs / actual players.

As in, what level can a PC be in a 3.P game for a Murder case to be resolved by just "magicing" or "psionicing" an answer? How many evasive tactics do I need to employ before it just becomes too much? Is a challenging mystery one where the players pretty much give up and start asking for hints to point them where they should be? What is the best level to do this sort of game, or can any level work?

I have several more questions, but for now I'd at least like to here some people's experiences on running mysteries in D&D so I can have an idea of what to expect or work on for the game.

Any input would be greatly appreciated!

How much effort the murderer needs to have put in is partly determined by your party character level.

Assuming 9th level casting if available, here are the work-arounds:

Stopping ress:
1 Have the murderer disfigure, dismember, or burn the corpse - prevents anything but true ressurection.
2 Have the murdered have a 'reason' not to come back to life or respond to the PC ressurrection spell. Souls aren't required to come back, and you can't compel them to and they are aware of name, alignment and patron deity (if any) of the character attempting to revive it. (PHB 171)
3)If it's this high level, murderer uses trap the soul to prevent revivification (PHB 171)

Preventing easy-bake identification:
1) Have the murderer wear a disguise - this circumvents most any and all information gathered from the corpse.
2) Have the murderer employ a lacky - someone paid, charmed, or dominated who does not know who the killer is. The lacky can be found, but not their employer. (When combined with 1, you're down to logic)
3) Give the potentials high will scores (have it take place in a monastery) where almost any mind magic is basically going to fail.
4) Give a time limit and no fore-shadowing to the players. If the PCs aren't expecting to have to solve a murder, they won't prepare their list of spells ahead of time.

What not to worry about:
20 question spells: These are essentially limited to yes/no answers and if there are easily more suspects than questions it'll be a great way to waste the pcs time. Furthermore, since the answers are up to DM interpretation one could argue that the answer to: 'Did Bruce the guard kill Billy the helpless orphan?' is at once both Yes 'and' No if Bruce was responsible for protecting the innocent, by failing his duty, he killed Billy.

Remember, there are alot of motives for killing that don't make a character evil, and being evil doesn't mean you ever actually harm anyone. So feel free to provide red herrings for detect evil and chaos.

Other possibilities:
Hiding parts of the mystery with Sequester, Nondetection, or Obscure Object. This could be as easy as pendents of nondetection being common magic items.

Edit: another idea is to have the victim be in on it (hence they know who will be true ressurrecting them and won't accept it until that occurs. Perhaps the 'victim' is themselves a killer who is dead until the heat dies down).

[Toliudar]

Gentleperson's agreements aside, I'd just start everyone at 1-2 level for a mystery campaign.

[Chained Birds]

It seems like Spells are the main problem.

What if the game was pure Psionics (Or mainly Psionics where magic was outside the norm)?

[NichG]

Or run it in E6, so these things never become an issue. You can run mystery games for Lv20 characters, but they have to be mysteries that even the gods don't know the answers to. Rather than 'who killed this man', its 'who contrived to eradicate the worship of Apophis' or 'why is the plane of Baator missing a layer?'.

Also psionics has Hyperconsciousness or whatever its called, which is basically 'read the DM's plot and setting notes' in the form of a psionic power.

[Chained Birds]

The Alexandrian blog has some good tips for running a mystery. If you follow this links to other posts, you'll get some really good advice:

http://thealexandrian.net/wordpress/1118/roleplaying-games/three-clue-rule

Oh, this looks like a great read. Might help iron out some of my plans.


The single most important prerequisite is that your players have to want to play a mystery game. If they don't, they'll break out all the cheaty-magic stops and/or sit there and stare at you until you give them answers.

The second consideration to look at what your players can, potentially, do... Design the mystery around your players' abilities, rather than cutting their abilities around to fit the mystery.

I have no plans to force anyone into a game that they are not interested in. I would most likely test this idea out on these forums, so only people who want to play will play.

[ZamielVanWeber]

The Bard spell selection makes for excellent criminal activities. Glibness cuts through truth spells, as does Disciple of Mammon's class feature (they also get non-deteftion later, and a buff to bluff). Charlatan's master of lies causes all divinations to only find their assumed persona. That is open ended enough that a NE faking LN sorcerer could hide her crimes behind her EX ability.

[Raimun]

The kind of people who challenge the minds of Sherlock Holmes or Hercule Poirot can't challenge normal D&D roleplayers with access to mind reading, Speak with Dead or Divinations in general. For example, the PCs have found the murder weapon? There exists a spell that specifically tells the item's history to the caster. Case closed.

The only obstacle would most likely be the laws of the land. They might not view spells as legal evidence. ... Yet, the PCs can still assassinate the guilty one and the case is still closed.

The only way to give challenging mystery cases for PCs with powerful magic is to use powerful magic. Basically the only possible people who could challenge the minds of the PCs are people like archmages or high priests who commit the perfect crime by masking their involvement with magic... and even that narrows it down, since only they could do it.

The true mystery is how there can be any mysteries in the first place.

[Grod_The_Giant]

The kind of people who challenge the minds of Sherlock Holmes or Hercule Poirot can't challenge normal D&D roleplayers with access to mind reading, Speak with Dead or Divinations in general. For example, the PCs have found the murder weapon? There exists a spell that specifically tells the item's history to the caster. Case closed.

The only obstacle would most likely be the laws of the land. They might not view spells as legal evidence. ... Yet, the PCs can still assassinate the guilty one and the case is still closed.

The only way to give challenging mystery cases for PCs with powerful magic is to use powerful magic. Basically the only possible people who could challenge the minds of the PCs are people like archmages or high priests who commit the perfect crime by masking their involvement with magic... and even that narrows it down, since only they could do it.

The true mystery is how there can be any mysteries in the first place.
There are plenty of things that a clever crook can do without magic. Speak with dead, for example, requires that the corpse have a mouth to be able to talk. Twenty seconds with a light mace can solve that problem. Legend Lore? Throw the murder weapon into a furnace. Commune? "Unclear" is a legitimate answer-- and you need to be a suspect before PCs will think to ask about you.

Sure, you have to be clever to avoid higher-level magic, but you should be facing someone highly competent at that point.

[Peelee]

Something I don't think anyone has proposed this far would almost completely negate any spells the players have without bad DMing, cheating, or running low-magic campaigns. Go Columbo with the mysteries. The players can fully and truly know that it was Jeff who murdered Bob, but PROVING Jeff did it is the actual challenge. Sure, a quick Commune or Speak with Dead spell could solve the who in the whodunnit, but the courts could not allow such as legal evidence, since other magic exists that could easily fake such evidence (a corpse could be Magic Mouthed, for instance, and thus able to give "false testimony"). If the players cast Commune and find out Jeff killed Bob, that's great and all, but Jeff is still running free and they still have to prove he did it. You could actually watch some Columbo episodes to get some ideas of how to pull of tricky murders (Columbo is pretty much all murder, if I remember, so other crimes, you're on your own) if you needed inspiration. Search results could turn up several false clues or red herrings in addition to the actual clue. The only thing to keep in mind here is to not make it too hard - not everyone is an actual detective, and one of the first things I learned as DM was "no matter how blatant you make it, if you want the players to deduce A from the evidence, they will invariably deduce B-Z.

[Raimun]

"OK. Well, this all seems in order, so I guess I'll- oh! Wait. You seem to have made a mistake right here."

"Aw man! What's the mistake?"

"I'm Chaotic."

Columbo style is fine but that assumes people who carry out the inspection work within the legal system. :smalltongue:

[Rhynn]

Columbo style is fine but that assumes people who carry out the inspection work within the legal system. :smalltongue:

Any mystery set-up assumes a lot of things about the... well, set-up. :smalleek: Working outside legal systems is potentially pretty dangerous, particularly in settings where the above-discussed issues with secrecy exist...

[Seharvepernfan]

So I plan to one day run a mystery-type game where the PCs would play as detectives trying to solve various cases, from murders to unexplained phenomena. The trouble I'm having is creating these mysteries or at least determining the challenge of a particular mystery vs the capabilities of the PCs / actual players.

As in, what level can a PC be in a 3.P game for a Murder case to be resolved by just "magicing" or "psionicing" an answer? How many evasive tactics do I need to employ before it just becomes too much? Is a challenging mystery one where the players pretty much give up and start asking for hints to point them where they should be? What is the best level to do this sort of game, or can any level work?

I have several more questions, but for now I'd at least like to hear some people's experiences on running mysteries in D&D so I can have an idea of what to expect or work on for the game.

Any input would be greatly appreciated!

Familiarize yourself with all the skills and spells in the PHB. Take the time and do it, if you haven't already.

Now, look at your campaign world and its' level of magic/leveled-people/etc, and really think about how that's going to affect your mystery adventures.

I don't know where to start, so I'm just gonna jump in somewhere random.

1. Timing. How long has it been since the crime/event happened? This can make a lot of differece. Survival-track is dependent on time, especially if using scent. Certain divination spells only go back so far. Casters need time to prepare the right spells. In a less mechanical sense; people have limited memories, so if it's been a while since something happened, they will remember it less and less. Also, people involved or witnessing crimes have a tendency to disappear after a period of time.

2. Where. An event that takes place in a stone room in a crypt somewhere is probably not going to have any witnesses, but the evidence should be pristine. An event that takes place in a crowded marketplace is going to have tons of witnesses, but the evidence is going to be extremely "corrupted".

3. Why. Was the event planned, was it spur-of-the-moment, was it an accident? What was the motive?

4. Who. Who did it? Who was involved in it? Who knows what? Who lied to whom? Who is lying to you? Who is involved, but doesn't realize they're involved?

5. Skills. Bluff is obviously a big one - even a lowly commoner can pull off a lie if it is believable and the target wants to believe it. Sense Motive is another big one - not just to detect a lie, but also to determine if someone is trustworthy, if they are charmed or dominated, or if something about the situation just isn't right. Gather Information can spread rumors as well as find them. Disable device can cause saddles/wagon wheels/various-other-things to fail unexpectedly. Open lock can get you in and out of places without showing signs of entry. Heal can determine cause/time of death.
Know: arcana and spellcraft especially can be very useful in magical mysteries.
Disguise, intimidate, diplomacy, know: local/history/nobility & royalty, forgery, sleight of hand, search - all highly relevant to certain mysteries, and are often combined in a single crime.

6. Spells. On both sides of a crime, spells are very important. Many spells can obscure a crime, and many can reveal it. Explaining them in depth would be a thread of its' own. More importantly, how available are the various spells to the people involved in the mystery? Every spell has a counter, if only it's available to the person in question. Can the person cast the spell themselves? Can they cast it from a scroll or wand that they bought or stole? Can they hire someone to cast it? If so, from where? And what did it cost them? Were there strings attached?

7. Monsters. Dopplegangers, mindflayers, vampires, fiends, dragons, and various other insidious monsters can make solving a crime into a maddening experience (not to mention extremely dangerous). Their innate abilities make them well-suited for crime.

Whether or not a mystery is challenging depends mostly on the players themselves, but also on the abilities of their characters.

A highly-skilled player playing a fighter can probably solve a crime better than a novice/idiot player playing a genius rogue/bard/cleric/wizard/ranger/whatever.

If all it takes is the use of a single skill or the casting of a single spell, then it probably wasn't much of a mystery. However, not every mystery needs to be great, in fact I'd say that most don't. Expending a spell to learn something potentially vital is a good use of a spell. If a character invested in that skill/spell, then they should reap the benefits.

When creating a mystery:
1. Pick a "prometheus"; the character who intentionally or inadvertently started the mystery.
2. Decide a motive; why did they do what they did?
3. Method; how did they do what they did?
4. Location; where did they do what they did?
5. Complications; what can make it difficult for the prometheus to pull off his mystery? what can lead the hunt to them? what can make it difficult to lead the hunt to them? Are there any second or third parties? Does the prometheus know of them?
6. Proxies? Did the prometheus use any toadies/goons/mooks/henchmen to get the job done? How many? How many layers of henchmen are there? (prometheus hires as assassin, the assassin hires some street thugs, etc.) Are they duped into participating? Were they coerced?
7. Dynamics; how are you going to throw it all together in an exciting and explosive (or subtle and devious) way? Massive three of four party battle in the crumbling remnants of the still-highly-explosive powder-mill with a cultist on the roof actively summoning a fire demon during a thunderstorm? The mayor getting poisoned in his bed the night after the big ceremony, after the party was rewarded for catching the "assassin" in that gigantic cluster-frick at the mill?

Don't spend too much time thinking about how difficult the mystery is for a group of players. In general, the more focused their builds are on combat, the less capable they are of solving mysteries. If they're combat gods, either keep the mysteries simple or expect them to be incapable of solving it on their own. If they are particularly well-rounded, you can throw just about whatever you want at them.

If the key-suspect ran off in the woods after committing the crime, and no one in the party has the track feat, they still have many options. Is there a tracker/hunter they could get to track for them? Do they have any animals that can track by scent? Can they acquire any? Can the party speak to animals who may have seen the criminal? Are there any fey creatures who can help out, if coerced into doing so? Can the party hire a diviner or a priest to determine where the criminal is? Can they guess where the criminal went? Can they just hire a detective if it comes to it?

A few more miscellaneous tips:
1. Your party is not going to do what you expect. Expect this.
2. They're going to miss your hint. Throw in several.
3. Leave at least three openings for the players to succeed, otherwise your adventure may crumble before it gets off the ground.
4. Play npcs' to their intelligence/wisdom/personality/training/background/alignment - don't be afraid to play evil people as evil.
5. Hook your players with potential rewards and/or by making it personal.
6. Vary it up. Crack open those books and use all sorts of stuff to make the adventure dynamic and interesting.
7. Add in a few complications or unrelated side-events to keep things interesting; chasing the assassin through the forest at night when werewolves/bandits/wild-elves attack (could even attack while you're fighting the assassin, turning it into a three-way battle).

I think that's about all I've got. Hope this helped.

[Duke of Urrel]

I have run two campaigns like mysteries – though admittedly, these were done for first and second-level PCs.

I don't believe it is really that easy to solve a mystery by Divinations alone. Most of them allow the DM to give cryptic answers, or even none at all. The gods themselves don't want to make things too easy for their minions. The truth must be earned!

Yes, you can Speak with the Dead, but that only gets you an eyewitness account. If the murder victim was killed in the dark, maybe he didn't see the killer all that well. In one of my mysteries, Oil of Taggit played a role –*an ingestible sleeping toxin that's tasteless and odorless and knocks you out one minute after you drink it. Did the victims of this poison know who slashed their throats while they were asleep? No, they did not.

[Gavinfoxx]

A mystery game should probably max out at level 2.

Consider spells available at character level 3:

Detect Thoughts, Locate Object, Sentinel's Watch, Vision of Fear, Insidious Insight

[Story]

Gather Information can spread rumors as well as find them.

Where are the rules for this?

[CoffeeIncluded]

Maybe you could have people flat out-refuse to give you straight information, or any information at all, out of fear for their own safety. At least, that could be a confounding variable.

[Seharvepernfan]

Where are the rules for this?

Look up Gather Info on pg. 74 of the phb. In the first paragraph is says:


Use this skill for making contacts in an area, finding our the local gossip, rumormongering, and collecting general information.

[Duke of Urrel]

Maybe you could have people flat out-refuse to give you straight information, or any information at all, out of fear for their own safety. At least, that could be a confounding variable.

This is good advice, and the description of Gather Information skill itself refers to "obvious reasons why the information would be withheld" as a possible limiting factor.

As a DM, I try to avoid giving PCs nothing at all when they make a really good skill check, but when necessary, I put limits on Gather Information skill by giving incomplete or cryptic information – that is, clues or leads – rather than straightforward answers. It's usually not necessary to deny the PCs all the information they're looking for, only some of it. Give enough of a clue to lead the PCs to the next clue, which leads them to the next, and so on.

Work backward from the PCs' ultimate goal by devising a final clue that leads to it. Then come up with the second-to-last clue, the third-to-last, the fourth-to-last, and so on. Hide the clues (and some knowledgeable informants) in dark, dangerous, and hard-to-reach places. The game becomes like a scavenger hunt. As Seharvepernfan said in a very helpful posting, hardly any method for finding or divining the truth is absolutely infallible, so it's necessary to use multiple clues that can be found in multiple ways. Gather Information skill is only one of those ways.

It's true that Divinations can reveal a lot beyond what Sherlock Holmes could ever discover, but without some information to start with, not even a high-level spellcaster can know whose mind to read, whom to scry upon, or which object is an important clue. Clever criminals use decoys, Abjurations, the Misdirection spell, interplanar escape routes, and other tricks to keep ahead of detectives. Besides, most Divinations allow the DM to give riddles or puzzles rather than simple answers. I think with a little planning and counter-magic strong enough to resist the PCs' own magic, some mystery can be maintained even for higher-level PCs.

[Alienist]

Maybe you could have people flat out-refuse to give you straight information, or any information at all, out of fear for their own safety. At least, that could be a confounding variable.

I operate on a couple of principles for information gathering:

(1) NPCs (especially those with hidden agendas) can lie
(2) If you ask someone random for information, the information you get will be random

D&D (and other RPGs) often operates on the assumption that if you roll high enough you can walk up to a random medieval peasant and they will give you the design for a hydrogen bomb, hyperspace engine schematic, or intimate knowledge of the big bads dietary requirements and an up to date layout of his lair and traps.

I, on the other hand believe that if you want those things you should be asking a nuclear physicist, time traveller, nutritionist and the architect of the castle (respectively).

Since knowing who (and what) to ask is so important, that should be the first question.

The reason that the RPGs do this is because typically they are a sausage link of clues that you have to follow. If you miss even a single sausage the entire adventure grinds (sic) to a halt.

To avoid that you should have more than one thing going on at a time.

As for the NPCs never lying, I even had one group who always treated their own allies as inherently unreliable, but whatever the bad guys would tell them was the gospel truth. Weird. I think some other DM broke them before I got ahold of them.

[Story]

Asking the right person is supposed to be abstracted away with the Gather Information skill.

[NichG]

Different abstractions are appropriate for different focuses of the game.

That aside, Gather Information isn't a sovereign solution because it takes a long time even if you're very good at it, and the quality of the information you receive is strictly limited to 'the grapevine' kind of things. You can't always 'gather information' directly on who killed a guy unless it was a mob hit or something like that, because it may be that the only person who knows is the killer.

This does bring up a point. If you're going to run a mystery campaign, you should absolutely write up a blurb describing how things generally work in a mystery, including how you expect skills (and common/expected spells) to interact with the process. If you make it clear how Gather Information is going to work in your campaign, its a lot less problematic to the players then when you spring on them that their skill doesn't do what they think it does.