Mike at The Feces Flinging Monkey notes that an American lawyer was imprisoned for 2 weeks because his fingerprints were mistakenly matched to a latent print found on an item used by terrorists.
That’s what I used to do when I worked for the police. Fingerprints, ID, stuff like that. I figure you guys would like to hear an opinion from someone with some practical experience.
So far as prints are concerned, they are 100% reliable when it comes to an ID. There are some people who have a problem with this, but that’s the way it is.
That doesn’t mean that there’s not false matches, though. The problem lies in the quality of the prints themselves, either the ones taken from the person you want to ID or from items and surfaces found at a crime scene.
One of the biggest problems I had was with crack addicts. They’d use glass pipes to smoke the drug, the smaller the better so the pipe would be missed in a search. They’d heat up to some really impressive temperatures, and the addict would be so high after the first puff that they wouldn’t be able to feel their fingers cooking.
This meant that most of the print would be burned off by the time I got them. Even so, there would almost always be enough detail to make a positive match. If there wasn’t we would just wait, since fingerprints grow back unless the skin is very horribly scarred. And if it was too scarred to read the print, well, even scars on fingertips have enough fine detail to make a positive match.
The other problem lies with latent prints. These are prints found out in the wild, so to speak. There’s no telling who left the prints, or usually when they were left, so the fingerprint examiner focuses on objects that had to be used to facilitate a crime. Find a print on a weapon or object used in a crime and that would go a long way to proving guilt.
But the world is imperfect, and most people are in a hurry when they’re committing a crime. So the vast majority of latent prints are smeared or obscured in some way. This can also be due to a bit of fumbling while lifting the print from the surface where it’s found as well as environmental factors.
But there’s standards to make sure that this doesn’t happen. The print has to have a certain amount of detail, a finite number of distinct features visible, before it can be used as evidence.
It looks to me like the latent print itself didn’t have this level of detail. So the latent print examiner at the FBI put it through their AFIS computer to see what the machine could do with it. When it came up with a match they picked the one that looked most promising and sent the data along.
This might not be as sinister as it seems. I don’t have access to the evidence files, so it could very well be that they simply told the Spanish intel guys that it looked like this lawyer was involved, and someone should explore that avenue of investigation. Then it would be over zealous Spanish cops who decided to pull the suspect in.
But this doesn’t excuse the FBI in any way. Like I said, there’s standards that they’re supposed to follow, and it’s obvious that they dropped the ball. If they didn’t have enough detail to make a positive match they should have simply said that they couldn’t do anything with the evidence and let it go at that.
The point I’m trying to make is that it’s not the system of using fingerprints as an ID tool that’s faulty here. Instead it’s human error that screwed everything up. Cops are people too, they make mistakes, and they really want to catch the bad guys. The problem is when they don’t follow the rules and try to make shortcuts.