Is it true that there is no scientific evidence that everyone has a unique fingerprint?

[Unity+]

There are some people claiming that there is no scientific evidence that suggests that everyone has their own unique fingerprint, which is important for criminal investigations. Is this true? I hope I posted this topic in the right section.

[Phi for All]

I think this is one of those issues where science doesn't go about things the way a lot of people think it does. Just like we use theory instead of proof, we look at the preponderance of evidence in the case of fingerprints and state that we've never found two people with identical fingerprints, which leads us to conclude that fingerprints are most likely unique to the individual. Pop-sci and the entertainment market often take that as "proof",

 

Then someone finds two identical snowflakes, so the whole idea of fingerprints being unique is thrown into question.

[Greg H.]

The problem with the claim is that there is an inherent flaw in the way it's worded. "Prove to me no two fingerprints match" is like asking someone to prove there are no magical grains of sand on earth - it's an impossible task without devoting an equally improbable amount of resources to the task.

 

What we do have is a proponderance of evidence that no two people have ever been found to possess the same fingerprints despite the literally millions of fingerprints available for comparison in databases currently. Even identical twins will possess unique fingerprints.

 

At issue, however, is the method of comparison. If the resolution of the comparison method is poor enough (i.e. if the raw fingerprint is only a partial print, or the print is of poor quality or degraded, or if the algorithm doing the comparision is not precise enough) false positives could be generated.

[swansont]

From what I can tell it's a statistical claim, much like that of snowflakes, because the conditions for formation will never be identical. It's not genetic- identical twins do not have identical fingerprints.

 

There's a second prong to the argument, though: that of how the fingerprints are used in criminal investigations, and how fallible that process is. Also, the difference between "matching" and "identical". Here's a good read on that issue http://www.psmag.com/legal-affairs/bias-and-the-big-fingerprint-dust-up-3629/

 

AFAICT the law enforcement folks have resisted rigorous testing of the reliability of fingerprint examination. There have been similar issues with the statistics of DNA matches as well.

[Unity+]

AFAICT the law enforcement folks have resisted rigorous testing of the reliability of fingerprint examination. There have been similar issues with the statistics of DNA matches as well.

The difference between 'identical' and 'matching' does clear up my confusion. When a person claimed 'identical' I assumed they meant 'identical', not 'matching.' As I know of, there isn't evidence that there are two identical finger prints(though correct me if I am wrong).

[swansont]

The difference between 'identical' and 'matching' does clear up my confusion. When a person claimed 'identical' I assumed they meant 'identical', not 'matching.' As I know of, there isn't evidence that there are two identical finger prints(though correct me if I am wrong).

 

Right, but there's an implication that the uniqueness hasn't been conclusively established, either. I think there's good reason to believe it's true, but nothing I've read has cited any scientific study that lays it out.

[Marshalscienceguy]

There are some people claiming that there is no scientific evidence that suggests that everyone has their own unique fingerprint, which is important for criminal investigations. Is this true? I hope I posted this topic in the right section.

 

Fingerprints themselves are considered scientific evidence for solving a murder based on the fact each person has a unique prints. So doesn't that mean they were already proven valid at a previous point and time?

[studiot]

Hello Unity+,

 

It is not clear whether this is a science or legal question, but seems to be more legalistic.

 

In science(particularly mathematics) we have (dis)proof by counter example.

It only takes one counterexample.

 

In UK law we distinguish between Civil matters and Criminal matters.

 

The big difference is the amount of proof required, called the 'burden of proof'.

For Civil matters the burden of proof is substantailly lower.

 

The common phraseology is

 

In Civil matters the burden of proof is decided upon "The balance of probabilities" (in the evidence presented)

 

In Criminal matters the burden of proof has to be "beyond reasonable doubt", which is much more onerous.

 

However the burden of scientific proof is substantially higher than either of these.

[StringJunky]

Movement of the foetus in the womb, amniotic fluid density, rate of growth and final size influences finger ridge formation so the chances of two people being analytically alike in this feature is probably vanishingly small I would think.

[swansont]

 

Fingerprints themselves are considered scientific evidence for solving a murder based on the fact each person has a unique prints. So doesn't that mean they were already proven valid at a previous point and time?

 

That's the question: was that ever shown to be true?