How Fallible Is Forensics?

Apr 23 2012 @ 11:29am

Frontline examines the flaws in fingerprint analysis:

[Cognitive neoroscientist Itiel Dror] asked five fingerprint experts to examine what they were told were the erroneously matched prints of [Brandon Mayfield, a lawyer incorrectly matched to the Madrid bombing]. In fact, they were re-examining prints from their own past cases. Only one of the experts stuck by their previous judgments. Three reversed their previous decisions and one deemed them "inconclusive." Dror’s argument is that these competent and well-meaning experts were swayed by "cognitive bias": what they knew (or thought they knew) about the case in front of them swayed their analysis.

The series also shines light on shady forensic certifications. Maggie Koerth-Baker widens the debate:

Science in fiction affects our ability to understand science in real life. For instance, you might already be familiar with the idea that detective shows on TV, particularly forensics shows like CSI, might be influencing what juries expect to see in a courtroom. This is called the "CSI effect" and it's hotly debated.

Some prosecutors think it has a real impact on jury decisions—if they don't get the fancy, scientific evidence they've been conditioned to expect then they won't convict. Meanwhile, though, empirical evidence seems to show a more complicated pattern. Surveys of more than 2000 Michigan jurors found that, while people were heavily expecting to see some high-tech forensic evidence during trials, that expectation probably had more to do with the general proliferation of technology throughout society. More interestingly, that broad expectation didn't seem to definitively influence how jurors voted during a specific trial. In other words: The jury is still out.