Picture this: Detectives on “C.S.I.” are on the trail of yet another mystery killer. The case goes cold, until a crime lab technician matches a small bloody fingerprint found on a torn dress. Suddenly the killer is ID’d, and the case is closed, just in time for the credits!
It’s a plot twist we’ve seen thousands of times in recent years, but of course, real life doesn’t work that way! So let’s separate some crime lab fact from fiction.
First: Is there really a fingerprint database that detectives can access at the push of a button? The answer is “yes.” But it’s not nearly as fast as you see on TV. The current federal database holds over 53-MILLION fingerprints. And even with super-fast computers, the most basic search takes at least 2 hours to run!
Okay, but once the search is done, police get a match and the case is closed, right? Actually, it’s NEVER that easy, according to Detective Wieners, computers don’t give one single match like you see on TV. Instead, the system spits out a list of possible matches, then it’s up to an expert technician to narrow the list down to a few likely candidates. But even if they find a close match, usually there needs to be more evidence.
Something else to keep in mind: Only 26 percent of all fingerprints lifted from a crime scene are even usable in the lab. All too often, prints get smeared or distorted to an extent where they can’t be read by the computer. And before a print can be scanned, technicians have to carefully edit the image to remove things like dirt and fibers. One stray piece of dust can reduce the accuracy of a match by 30% percent!
In other words: The next time you watch “CSI,” enjoy the entertainment value – not the crime scene accuracy.