Once upon a time, forensic scientists believed that they could determine who killed someone by the last image left on the victim’s retina. Nowadays we understand why this is ridiculous, but at the time people believed that the human eye worked like a camera, with the retina acting like film, and that the last thing a person saw before their death would be retrievable by removing the eyes and examining the retina. Crazy, huh?
Unfortunately, some forensic techniques used today are also scientifically questionable. We see them used to great effect on shows like CSI, when in truth they’re actually a lot less legitimate than we’re led to believe. This Frontline article lays out which techniques are scientific, and which are less so. Fingerprints? There’s no scientific proof that everyone’s fingerprints are unique, and examiners can be biased by context. Firearm identification? Apparently the idea that a bullet can be matched to a specific gun relies on assumptions that may not be valid. Arson investigations? For years it was taken as truth that certain burn patterns indicated certain things, like accelerant. People have been convicted and even executed on the basis of such evidence. Now, it looks like those “facts” were bunk, and that signs thought to be absolute proof of arson can be produced through natural combustion.
All of this is frankly terrifying. On the one hand, it’s horrible to think that people who were innocent have been jailed, or even executed, due to faulty, unscientific forensic techniques. On the other hand, how do we even go about catching and convicting the people who have actually committed these crimes?