I recently came across an interesting article, discussing the evolution of the popular phrase “Better that 10 guilty men go free, than 1 innocent man go to prison.” More specifically, it discusses how the exact ratio has varied throughout all of human history. A perfect demonstration that as poetic as the phrase may sound, coming up with an actual number that’s well reasoned and justified, is almost impossible.

One annoyance of mine is that in all these discussions pitting innocent convicts against guilty criminals who go free, one factor rarely ever comes up: innocent men (and women and children) who fall victim to crime.

One of the most valuable roles of the justice system is to be a deterrent. “If you commit a crime, you will be put in prison, so don’t even think about it.” If you’ve ever witnessed schoolyard bullying in action, that’s exactly what every single day in adult life would also look like. At much higher stakes. If not for the justice system. By deterring would-be-criminals, it keeps innocent people safe, without even having to send anyone to prison.

Except that it isn’t a perfect deterrent. Crime is still a major factor in society. To give just one example, 15% of women in America have experienced rape at some point in their lives. To put that in real terms: if you have a mother, a sister, a wife, and 3 daughters or nieces, one of them is likely to be a victim. And then there’s robbery, assault, manslaughter, homicide… the list goes on.

Some crimes are committed by those who’re mentally unstable, or in the heat of the moment. But the vast majority are committed by criminals who are fully aware of what they are doing. People who think they have a good enough chance of getting away with it. People who would never do it if they knew for sure that they would go to prison.

For some reason, people refuse to believe the above. Perhaps they are overestimating the role of mental illness in crime. Or perhaps they think criminals are so stupid that they will knowingly do things that will land them in prison for years. Regardless of what people’s intuitions may lead them to believe, the evidence is clear. Here are some quotes from a study investigating the matter.

If there was 100% certainty of being apprehended for committing a crime, few people would do so. But since most crimes, including serious ones, do not result in an arrest and conviction, the overall deterrent effect of the certainty of punishment is substantially reduced. In reviewing macrolevel studies that examine offense rates of a specific population, the researchers found than an increased likelihood (certainty) of apprehension and punishment was associated with declining crime rates. Similar findings are observed in micro-level studies on deterrence that assess the likelihood of individuals engaging in crime. People who perceive that sanctions are more certain tend to be less likely to engage in criminal activity. Increasing the probability of apprehension by 10% was predicted to reduce the likelihood of drunk driving by 3.5%. Most studies suggest that certainty of punishment is related to reductions in crime rates.

The majority of criminals either think they won’t get caught, or even if they did, that they can find some weakness in the prosecution’s case that would allow them to beat the rap. And the likelihood of the latter really comes down to how high the burden of proof is. A guilty person is much more likely to be acquitted in a legal system that is willing to exonerate 10 guilty criminals, in order to spare 1 innocent man.

As the above studies have shown, the better the chances of getting away with it, the less it would deter would-be criminals. Which means you’re going to have more victims of crime. More victims of assault, kidnappings, rape and murder. Which is really what the tradeoff should be all about.

“It’s better that N innocent men be murdered, than 1 innocent man go to prison.”

Now what would your answer for N be?