Is that relationship not manifested by the fact that smart crimes are not being discovered or recorded nearly as often? 
If you have a motive, they'll tend to figure this out and find the evidence to convict you. This holds people back who can foresee consequences, even if some moral notion does not. The decent chance of being caught makes the risk/reward ratio of most crime seem unattractive to those who can think critically about the matter.
I mean, consider that you want a particular person dead. You surely have some good reason for this desire, which can be sniffed out in an investigation. This means you will be under the microscope if this person actually does turn up dead, whether or not you did the deed. How easy would it be to pull off the caper then, in this day and age, without leaving one fingerprint, one molecule of DNA, one witness, one security camera getting you on tape, without leaving anything tying yourself to the weapon? The amount of work alone would be enormous, apart from the risk. Even if you commit the "perfect" crime somehow and nothing can be proven, you can expect to defend yourself in some way, shape, or fashion for it, which would cost time and quite possibly a great deal of money. And note you will be tried by 12 of the dumbest people in your community.
Even if not convicted, your community would likely assume you did it anyway, with social repercussions. Besides, if you don't get to look the bastard in the eye as you cross rapiers and pierce his heart, then what may I ask is the point?
Thus the intelligent person turns away from unlawful violence and simply prays for his nemesis to be struck with leprosy.
The real difficult ones to catch are those who commit crimes intelligently AND with no easily discerned motive, but like I say, the genius psychopath is far more common in Hollywood than real life.
