When you start thinking about the evidence that adds up to your life, you may believe that each piece - every memory, every object, every scar - is easily identified and contextualized. That the meanings and implications are clear. But even the most intimate experiences, the ones that leave traces on our skin and in our brains, can trick us. Even the most indelible impressions can shape-shift or fade. What seems obvious one year may feel ridiculous the next.
Even the hardest evidence can be called into question:
For generations, and until DNA came along, fingerprint evidence has been touted as the ultimate forensic tool. So unique and special are our fingerprints that DNA itself is often described as a "genetic fingerprint." And that essential truth remains. Done correctly, fingerprint analysis can be a powerful forensic tool of identification. The problem is that there aren't universal standards for what "done correctly" means ... This absence of basic uniform standards is the dirty little secret of Mayfield's fingerprint problem.
Fingerprint matches are made on the basis of what's known as "points of comparison," as a quick look at your thumb will demonstrate. What you will see are the friction ridges that comprise your unique fingerprint. The friction ridges whirl and spit, creating unique patterns that ultimately become the biometric data every burglar loves to hate. Comparing prints is a matter of looking for places where the ridges join or split—something that can be compared between prints. These points of comparison are used to both exclude prints (prove they are not the same) and to match prints. The problem is this: Print examiners and even the computers that do the preliminary scans don't actually match the entire print. In deciding if a print matches they almost always decide on the basis of a partial analysis. (Feige, 2004)
If a fingerprint is this elusive - this complicated and dangerous - then our memories (and memoirs) hold a potential energy far more lethal than we can imagine. This is why we need to play both sides of the system - prosecution and defense. We need to call our own cases into question, if we are ever to find the truth.
Feige, David. (2004). Printing Problems: The Inexact Science of Fingerprint Analysis. Slate. Available: http://slate.msn.com/id/2101379/