From a deterrence standpoint, I’ve never understood why there is such a thing as a necessity or duress defense in criminal law. The deterrence view of criminal law is that we choose punishments to deter judgment-proof individuals from committing acts that harm social welfare. If this is the case, then why bother with the necessity defense. A harmful act is a harmful act, whatever the reason it was committed. There is no reason to allow harmful acts because we think the reasoning behind them was good.
Suppose a car with a deathly-ill passenger races through a red light en route to a hospital. If the driver was “charged” with the crime, she could plead necessity and get off with nothing. But the fact remains that she went through a red light and caused social harm. Accidents are more likely because of the violated red, however good the motive behind the violation. So I would argue that we should get rid of the necessity defense in this context.
If we charge the driver with running the red light, then she would still probably run the light; the benefit of getting to the hospital sooner exceeds the cost of the ticket. In other words, the social benefit of the violation is greater than its cost. But this is not a reason for dropping the necessity defense. We want the driver to weigh the cost of running the light against its benefit. The best way to do that is to exclude the necessity defense and let the driver make the determination.
This analysis echoes the strict liabilityvs. negligence debate in tort law. The necessity defense is basically a negligence defense. The driver may have caused harm, but she wasn’t negligent, and therefore she should get off. I am arguing for strict liability. If you run the red, you pay the penalty, even if we think running the red was a good idea. When it comes to dangerous activities (such as running red lights), strict liability has some big advantages (such as its ability to engender efficient activity levels). Basically, dumping the necessity defense is the best way to insure that “desirable” crimes are only committed when they are truly desirable.