Do you let your villains make mistakes?

Whenever I design an adventure I often create flawed villains with exploitable weaknesses. This way, I have something for an inquisitive player character to uncover and use against her, or I have a few flawed personality traits that I can work into her encounter with the PCs. What I do sometimes forget is that my villains, like the heroes opposing them, can often fall prey to bad dice rolls.

I used to think that in order to challenge the players I needed my villains to set up almost-perfect crimes and only through collecting clues, successful skill rolls, and a bit of grey matter the PCs could overcome them. I’d be amused when a PC was on the right track but flubbed a skill roll or accepted a lie when interviewing a key suspect as it could sideline things until the PCs could get the investigation back on track. The villain laughed in her lair at the ineptitude, even if it was only a momentary setback.

And then one day I realized that the big difference between the PCs and my villains was that I was letting the villains make all of their dice rolls. I’m not talking about during confrontations, when I let the dice fall where they may along with the players, but before the adventure, when the villain needed them most to hatch her scheme. Why should she be immune to bad dice rolls?

From that point on, I’ve used this idea to help design my adventures. I’d come up with the villain’s plan and then I’d identify some key points where things could go astray. I’d then make the appropriate skill rolls and see how they play out. In some cases I’d pre-determine overrule the results, but in many cases I’d let the chips fall where they may and adjust the scenario accordingly. This not only made my villains (and associates) “play by the rules,” but it also enabled me to create the adventure organically.

For example, I once had a politician hire an assassin to take out a rival while he was staying at a hotel. This assassin was a sniper, but when I made his firearms roll he completely botched it. I decided that the intended target didn’t like his room for whatever reason and had it changed. The unfortunate traveler who got the room instead was assassinated. This added extra complications when the assassin tried to collect his fee from her employer (a resulting skill roll there had the quick-thinking politician contract another assassin to take out the first and then do the other job properly) and now, in addition to finding the assassin(s), the player characters also had to make sure that the target wouldn’t be killed in a follow-up attack.

This technique worked really well when I let the players in on how I created mysteries. They now look for mistakes when they investigate (and I admittedly go with them at times when they come up with something awesome on their own) and they consider it a real challenge when they come against adversaries that seemingly don’t make mistakes, assuming that the villain must be highly skilled.

How about you? Have you ever used a technique like this? Do you regularly seed mistakes into your plots? Has it ever been a problem?