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.
I had understood he was detained as a material witness on the basis of the fingerprint. I would assume there is a lower threshold of proof for such detention. Did I have the facts wrong or am I missing something?
“I had understood he was detained as a material witness on the basis of the fingerprint. I would assume there is a lower threshold of proof for such detention. Did I have the facts wrong or am I missing something?”
No, David, you’ve got it right. At least you do so far as US law is concerned.
But the cops just can’t lock you up indefinitely without charging you. At least they can’t in the US. I have no idea what the standards are in Spain.
James
But what are the standards when it comes to terrorism ? It has been argued that they should be different and much stricter, and law enforcement powers have been extended.
“But what are the standards when it comes to terrorism ?”
Really good question, Sylvain. I’m afraid that I don’t know, particularly when it comes to a foreign country.
I’d say that this incident will result in a lesser degree of co-operation between the FBI and the law enforcement agencies from other governments. Not that the FBI will turn down a request, but I think they will simply refrain from offering advice and stick to the facts.
And that’s the way it should have been from the start.
James
James,
Pretty weird that the guy was a convert to Islam, and his wife was foreign born, or did I read the story wrong?
Mike Schab
I’ve been hearing that he was held similar to a prisoner and some times held with criminals. Shouldn’t he have been held in a better environment?
“So far as prints are concerned, they are 100% reliable when it comes to an ID”
and
“That doesn’t mean that there’s not false matches, though.”
I can’t get my head around these too mutually exclusive assertions:)
Not an expert but I would say fingerprints are just another tool. And like all tools they will produce good or bad results depending on the skill and intentions of the people using them.
“I can’t get my head around these too mutually exclusive assertions:)”
They’re not mutally exclusive, you’re just confusing two related topics.
The prints are 100% reliable, period. It’s been that way for over a century. Every single test, every challenge to using fingerprints as an infallible method of ID, has been met and proven to be without merit.
But people make mistakes. That’s just the way it is. If the print is clear, with all of the details in the print nice and crisp, then it’s virtually impossible to make a bad match if proper procedure is followed. In fact, I’d say that a match that is confirmed through this method is as close to certain as you’re ever going to find in this life.
(What I’m referring to is the system of checks and counterchecks that are supposed to occur after the prints are taken. It isn’t just that fingerprint experts from the arresting agency check each other’s work, but they also pass the prints around and let other agencies check them against the files that they have.)
But the problem is when you’re dealing with latent prints. They are most often blurred, smeared or obscured.
This doesn’t mean that latents can’t be used for a positive ID. They can, as long as there’s enough detail showing in the print so the tech can match up a finite amount of corresponding points between the latent and the match.
In my department the standard was 12. Line up 12 points between the latent and the match and you had your man. Obviously, the print the FBI received didn’t have this level of detail.
So they should have returned the prints to the Spanish authorities and said they couldn;t help.
James