Red herrings appear to violate Chekhov's gun, but I've been told that not all red herrings are the same and it seems that some red herrings are OK if they serve some sort of purpose.
How do you ensure that a red herring doesn't violate Chekhov's gun? Can you give me a list of criteria a red herring needs to meet in order to not violate it?
Red herrings do serve a purpose: they (ostensibly) make it harder for the reader to identify the true culprit. They don't inherently violate Chekhov's gun, but you do need to, at some point, bring them up again in order to explain that they're red herrings.
For example, let's say you have a detective investigating a death by shooting, and they find three different guns that implicate three different suspects and could all have been used in the shooting. Two of those guns are red herrings, and the detective's summation needs to explain how they know that Gun A was used and not Guns B and C.
One of my favourite examples of a red herring is the What's New, Scooby-Doo? episode "Roller Ghoster", where an amusement park is being terrorised by a monster. There's an extremely obvious red herring in the form of a kid who keeps getting turned away from rides for being too short, and gets increasingly furious about it. At the end of the episode, after the monster has been caught and unmasked, the kid shows up and asks, "How come I wasn't a suspect?", to which Velma bluntly replies, "You're too short to fit in the costume". Had he not made that appearance at the end, it would have been a violation of Chekhov's gun.
(Before anyone brings him up, I know A Pup Named Scooby-Doo has a character literally called "Red Herring", but in most episodes he doesn't actually appear until Fred randomly accuses him at the end, so he's not relevant to OP's problem.)
F1Krazy’s excellent answer gives a first main principle: They should be well-explained as red herrings, sooner or later. I’d like to add a secondary principle, at least for classic detective/mystery style plots: Their status as red herrings should be foreshadowed before the main reveal. Not too obviously — they certainly don’t need to be fully revealed in advance. But if at the point of the main reveal the reader really had no way to pick between the true culprit and the decoys, they can rightfully feel a bit cheated: they weren’t given a chance to solve the mystery! Ideally, you want your reader to be unsure up to the main reveal, but by the end, they should be able to look back and see how earlier evidence pointed to the true answer and ruled out the red herrings all along.
Insofar as it’s a bad thing, “violating Chekhov’s gun” means setting up inaccurate foreshadowing; this is what leaves a reader feeling cheated. A well-written red herring involves accurate but misdirecting foreshadowing — things that appear at first to incriminate the red herring, but in hindsight point more towards the true solution.
The answer depends on how you interpret the principle of Chekhov’s gun, in particular what counts as firing the gun, and to what account you incorporate audience expectations and Chekhov’s gun itself into all of this:
On a basic level, the entire point of red herrings is to subvert Chekhov’s gun. If every story strictly adhered to Chekhov’s gun, certain plots (in particular whodunnits) would be boring: It’s much easier to figure out the solution if you know that every single hint is pointing towards it. Also, there is less room for an interesting conflict to arise from hints pointing in different directions. Red herrings solve this.
On the next level, subverting expectations of Chekhov’s gun is the purpose red herrings serve – and thus they are not unfired Chekhov’s guns.
From yet another perspective, one might consider a red herring an unfired Chekhov’s gun if it is not addressed to be a false lead on page. There is some merit to this, as for example, dropping an entire subplot hinging on a red herring is clearly unsatisfactory. On the other hand, if interpreted this way, Chekhov’s gun is merely a useful guideline, not a principle that you must strictly adhere to: In most forms of writings, you do have tons of details that mainly serve to create atmosphere and need not be picked up again. Specifically, addressing every slight hint that lead nowhere at the end of a whodunnit can just be an insufferable drag.
Thus, when creating and addressing red herrings, you have to balance between:
