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Junk Science and the Justice System

A disturbing new story on a murder trial in Illinois makes the case that we should be more worried about magical thinking masquerading as forensic science

The great promise of forensic science is that it's supposed to make justice more certain. Instead of relying on hunches and timelines and witnesses, cops and prosecutors can prove a suspect's guilt absolutely with DNA evidence, dental records, computer history, or any one of the myriad sources of personal information floating around about each of us. It's supposed to net the guilty without turning the innocent into bycatch.

In reality, it doesn't work that way. Study after study has debunked bloodstain pattern analysis, bite marks, field drug tests, and a variety of other forensic "tools" as unreliable at best and gussied-up pseudoscience at worst. That hasn't stopped courts from allowing prosecutors to regularly present evidence that's about as weak as dowsing (coincidentally, another thing that some police departments are training their officers in) or juries, primed by shows like CSI and true crime to trust any evidence presented with a veneer of science and authority, from believing it.

If we think it's important to keep wrongly-convicted people (who, I cannot stress enough, could include you, me, or really any one of us) from wasting their lives in prison, then it should be self-evident just how incredibly dangerous this embrace of junk science is. Rather than making the justice system run more clinically and precisely, it functions as a kind of legal philosopher's stone, allowing prosecutors and law enforcement to transmute their own biases and opinions into hard evidence. The Neflix documentary series Exhibit A delved into this subject, showing in different episodes how criminal defendents had ended up serving decades in jail based on as little as a cadaver dog signaling on a carseat.

ProPublica recently went deep on a case that epitomizes the pitfalls of bad science in the courtroom. Jessica Logan ended up becoming a suspect in her infant son's death because a police officer who had taken an (eight-hour) class on the (debunked) science of 911 call analysis decided she hadn't used the right words while calling for help after finding her 19-month-old stiff and cold in bed. That judgment colored police reports after the fact and, together with what ProPublica convincingly argues was a deficient autopsy, ended up landing her in prison for 33 years. This was a pretty chilling story that I hope gets the wide audience it deserves. Whichever way you land on the necessity or competence of the justice system, science that goes against the available evidence is just mysticism under another name, and no basis on which to ruin or end a human being's life.