As a matter of adventure design (or when improvising as a DM), you shouldn’t lock mission-critical information behind a skill check. Because if the characters fail the check, the plot line is dead.
But, the solution isn’t to get rid of skill checks.
The solution is DC 0 checks.
“Isn’t that basically just telling them the information?”
Yes, but we don’t stop there.
Progressive Skill Checks
The idea is to move away from binary skill checks to a progressive resolution system. So, you still have a check to discover mission critical information. But, the DC to learn the stuff you need to know is set at zero.
As you roll progressively higher, you learn additional information that isn’t necessary, but helpful. You probably could have found out that extra information eventually with your DC 0 clue, but rolling better lets you take shortcuts by applying more intuition or conducting a better search.
While you should seed a murder mystery adventure with multiple clues, each of them should be set as a DC 0 check, so that no clue turns up useless. But, depending on the amount you investigate a certain clue, you may glean more information.
Sherlock Holmes was famous for deducing more information from a crime scene than the professionals at Scotland Yard. So, make that opportunity available to your characters! As they walk in on the murder scene, the investigators have clearly identified that the victim died from the massive rending wound on their chest. But, further investigation of the scene provides additional illumination.
When writing an adventure (or preparing for your session), consider writing your skill checks into tables to avoid binary resolution states. Here’s a sample:
You don’t need to be this granular. You can set as many or few DCs as you want. You can set each DC at anything you think is appropriate. Maybe you have a lot of low-level information that you’re happy for a skill check to convey, so you set a bunch of low DCs. I also recommend doing the “dead giveaway” at a DC 30+, since that’s considered a nearly impossible task. Let your players shine for having invested in skills!
The important thing is to make sure the plot line isn’t dead. Give your players the mission critical information they need to keep the plot moving, at least in some direction.
Monster Knowledge DCs
Non-binary skill checks can also be used in other contexts. Check out ThinkDM’s Monster Knowledge DCs to see how we implemented a progressive skill check for players asking what they know about a monster. That one starts at DC 5 (no monster knowledge is mission critical), but it illustrates how the concept can be adapted to different aspects of the game.