4 Reasons A Lot of Forensic Science is Total Crap

Posted on May 17, 2012 by


Alright, I admit, that headline is a bit sensational. The science itself isn’t all bad, it’s how it gets used and the failure of the criminal justice system to be sensible about science that leads to science being misused.

So what’s gone wrong?

Image: Amazon

Stated conclusions far exceed the reasonable limits of the science. If you haven’t read John Grisham’s The Innocent Man, go buy a copy right now. To be sure, the real story is less about science and more about dishonesty, but in the book (non-fiction) we learn how experts take tentative findings and blow them up into rock-solid evidence. You know what’s really reliable? Most DNA evidence. Beyond that, a lot of forensic science doesn’t so much give answers as it suggests a relationship. These are not the same thing, but forensic scientists, eager to validate their own work and hold offenders accountable, routinely overstate the significance of their findings.

Criminal justice system professionals are ill-equipped to evaluate the merits of the science. Quick: if I told you that my results suggested that this piece of hair was so strangely colored that I would give it a z-score of +4, what would you say to me? A few will know enough to laugh, but on the whole, most people would say, “Um, okay.” And if I made my claim with gusto, you might say, “Wow, that sounds really impressive!” It’s not just that our society has failed to adequately educate its citizens in basic concepts like the scientific method and numeracy, it’s that, by design, the criminal justice system is populated with lawyers. Professional Arguers. Not Professional Examiners of Epistemology and Truth. And juries? Nope, they tend to have even less education than the professionals. So if you’re an expert, you need only sound just sophisticated enough that you make everyone else think you’re the smartest person in the room, and just folksy enough that you can explain your evidence as a story that anyone can believe in.

Credentialing can be paid for rather than earned. You have $500 extra bucks? Lucky you. You can run right out and buy yourself some fancy schmancy forensic examiner credentials. Are there real credentials that are worthwhile and meaningful? Well, shucks, so there are. But in the courtroom, who has time to get into which credentials are believable? Not to mention, even if the lawyers wanted to go down that path, they don’t really have the expertise to figure out whose credentials are bogus and who has bona fides.

The sexy aspects of forensic science encourage adoption without critical analysis. I’ll tell you a secret. Criminal justice professionals like CSI too. All of these television shows have glamorized forensic science to a degree that you start to think that all you have to do is run a fingerprint through AFIS and you’ll be younger, thinner, and with a more symmetrical face. I mean, forensic science is just that sexy, right? And because it’s so cool, has such great cachet, not many people are terribly interested in asking the critical questions. Has this been tested and replicated? Is anyone else using this technique? What kind of probability threshold are you using? How might this technique lead to false results? Whoa, wait, Horatio just put on his sunglasses… nevermind about all that. Can we time the length of his dramatic pause? I want to practice.

So the next time you hear about the latest sexy forensic science technique, don’t be too eager to enter into a willing suspension of disbelief. Be critical. And hope, for everyone’s sake, that criminal justice system professionals will be critical too.


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