Are Fingerprints Distinctive? | Math ∞ Weblog

On March 11, 2004 a sequence of bombs exploded aboard 4 commuter trains in Madrid, Spain, killing 192 folks and injuring 2050.

The Spanish police recovered a bag containing detonating gadgets which had a latent fingerprint that the Spanish shared with the USA Federal Bureau of Investigation (FBI).

The FBI apparently ran a test on the fingerprint utilizing the FBI’s Automated Fingerprint Identification System (AFIS). AFIS makes use of a sample recognition algorithm to generate an ordered record of presumably matching fingerprints.

One of many fingerprints on this record matched Brandon Mayfield, a Muslim American lawyer from the Portland, Oregon area. Skilled latent fingerprint examiners from the FBI proceeded to positively establish the fingerprint from the Madrid practice bombing as belonging to Brandon Mayfield; at the least, that is what the FBI claimed on the time.

Mayfield was arrested as a cloth witness within the bombing and an excessive amount of details about him appears to have been leaked to the press. In the meantime, the Spanish police matched the fingerprint to an Algerian man whom they arrested. The Spanish police instantly challenged the FBI identification of Mayfield, resulting in his eventual launch.

Mayfield later efficiently sued the FBI for his therapy.


A Single Fingerprint

Fingerprint identification has been in widespread use in the USA because the 1920’s the place standard tradition has, till just lately, held that fingerprints are distinctive. In response to some reviews, folks have even been executed based mostly solely on a fingerprint identification.

That is placing since most human and automated sample recognition skills and algorithms have important false optimistic and false damaging error charges. The writer had the expertise in 2002, previous to the Mayfield case, of attempting to find scientific research confirming the accuracy of latent fingerprint identification with out success. The truth is, there have been plenty of instances previous to the Brandon Mayfield case through which fingerprint identification was proven to have been flawed.

The suspect had an hermetic alibi. DNA assessments contradicted the fingerprint identification and cleared the suspect. These instances of incorrect fingerprint identification have at all times been blamed on fraud or error by the human latent fingerprint examiners relatively than a case of an identical fingerprints.

Some info about fingerprints. An identical twins often, maybe at all times, shouldn’t have the identical fingerprints. This implies a fingerprint take a look at can discriminate between the in any other case an identical twins. Dramatic demonstrations of this outstanding reality helped persuade juries within the 1920’s to simply accept fingerprint identification. Nonetheless, these demonstrations don’t represent rigorous scientific statistical research of the accuracy of latent fingerprint identification.

A small minority of individuals shouldn’t have fingerprints. Some folks have fingers with very shallow ridges which, in observe, makes fingerprint identification harder. Opposite to some claims, fingerprints might be altered by scarring and put on and tear. Automated fingerprint recognition algorithms have had substantial issues with individuals who work with their palms.

Discussions of the accuracy of fingerprint identification usually confuse the accuracy for comparisons of all ten prints, all ten fingers, and the charges for a single or a number of prints. For instance, automated fingerprint recognition algorithms have been very correct with all ten fingerprints in 2002 however a lot much less correct for a single print such because the forefinger or thumb. It’s troublesome to get all ten prints in the actual world.

Latent fingerprint identification is carried out by human examiners. There are automated fingerprint recognition packages equivalent to AFIS however these are in all probability not as correct as human beings. This isn’t uncommon. On the whole, human sample recognition skills are considerably higher than automated strategies based mostly on mathematical, statistical, or scientific strategies: synthetic intelligence, sample recognition, machine studying, and different synonyms.

That is one thing to bear in mind when scientists, attorneys, or others denigrate eyewitness testimony. Nonetheless, human sample recognition skills are imperfect. There are false optimistic and false damaging charges. Eyewitnesses do misidentify folks and objects. Human fingerprint examiners nearly definitely have non-zero false optimistic and false damaging charges.

Within the wake of the Mayfield case, an FBI Laboratory evaluation committee evaluated the scientific foundation of friction ridge examination (fingerprint identification) and really helpful scientific analysis together with a examine of the accuracy of latent fingerprint examiners (!).

The Nationwide Analysis Council (NRC) additionally recognized the necessity for evaluations of fingerprint examination selections in a examine in 2009. The FBI just lately printed a report on such a examine within the Continuing of the Nationwide Academy of Sciences (Accuracy and reliability of forensic latent fingerprint selections, PNAS, April 25, 2011). This examine discovered a 0.1% false optimistic fee and a 7.5% false damaging fee.

It’s price contemplating this for a second. Fingerprint identification is in widespread use in the USA. Individuals are routinely convicted or cleared of crimes based mostly solely or partially on fingerprint identification. Fingerprints have lengthy been portrayed and perceived as distinctive.

Fingerprint identification is often perceived as a extremely scientific type of identification. But fundamental scientific research of the accuracy of the method seem to have been missing till just lately. This lack has solely turn into obvious just lately as unfavorable comparisons to the seemingly rigorous statistical foundation of DNA profiling (previously referred to as DNA fingerprinting) have been made in addition to the intensive publicity acquired by the Mayfield case, a lot larger than earlier misidentifications which lacked the put up 9/11 terrorism angle.

The distinctiveness of fingerprints appears to be a kind of issues that “everybody is aware of” that has a remarkably weak foundation actually. Certainly, this appears to occur every now and then in supposedly fact-based scientific and engineering fields. A big variety of scientific and technological breakthroughs have occurred when somebody went again and questioned the underlying proof or information behind one thing “everybody knew.”

In most crimes, just one or a number of partial fingerprints are recovered, such because the thumb and forefinger used to carry an object, e.g. the bag within the Madrid practice bombing. There are over six billion folks on Earth. Suppose that one in one million folks have the identical or basically the identical partial prints; an examiner can’t inform the distinction. Because of this, actually, there could be about six thousand (6,000) potential matches together with the responsible occasion.

With cars, trains, and particularly air journey, it’s possible {that a} substantial proportion of those six thousand suspects reside inside touring time of the crime and lack an alibi. There was a small risk that Brandon Mayfield traveled secretly from Portland, Oregon in the USA to Madrid, Spain to take part within the bombings. Unlikely, however definitely potential. Even a really small false optimistic fee raises an affordable doubt.

Particularly because the Mayfield case, there was extra questioning of the scientific foundation of fingerprint identification each by authorities such because the FBI and the Nationwide Analysis Council in addition to in standard tradition. The TV present Numb3rs, mentioned within the earlier put up The Magical Arithmetic of Numb3rs, options an episode, in all probability impressed by the Mayfield case, through which a person is wrongly convicted as a consequence of an error in fingerprint identification.

Of their ebook The Numbers Behind NUMB3RS, mathematicians Gary Lorden and Keith Devlin have a chapter questioning a few of the mathematical foundation of fingerprint identification. DNA profiling is seemingly based mostly on detailed rigorous scientific research of the frequency of the assorted genetic markers used within the DNA assessments.

Comparable research appear to be missing the place fingerprints are involved, therefore the research of fingerprint identification that the FBI is now performing and publishing. The comparability between DNA profiling and fingerprinting has led to questions concerning the accuracy of fingerprint identification.

It could even be the case that questions concerning the scientific foundation of fingerprints could also be a means of promoting DNA profiling as a extra “scientific” and dependable substitute for now “quaint” (“legacy” within the parlance of the software program trade — often which means it really works and the market is saturated so we have to promote a brand new substitute know-how) fingerprint identification.

The uncritical acceptance of fingerprint identification for over eighty years, with out apparently performing ample rigorous research of the accuracy, illustrates the big hypnotic energy of arithmetic and science in our tradition. The favored picture of arithmetic and science is that they offer precise, black and white solutions.

“Scientific” assessments give dependable sure/no solutions. The Madrid bomber was Brandon Mayfield. The bomber was not Mayfield. There are not any false optimistic or false damaging error charges. Two plus two is 4, not 3.999 plus or minus 0.012. But, that is very hardly ever the case in the actual world. The truth is, one ought to nearly at all times demand to know the error charges of numbers and be suspicious of numbers quoted with out error charges or different {qualifications}.

Recommended Studying/References

Simon Cole, Suspect Identities: A Historical past of Fingerprinting and Legal Identification, Harvard College Press, Cambridge, Massachusetts, 2001

Accuracy and reliability of forensic latent fingerprint selections

Bradford T. Ulery(a), R. Austin Hicklin (a), JoAnn Buscaglia(b),1, and Maria Antonia Roberts(c)

(a) Noblis, 3150 Fairview Park Drive, Falls Church, VA 22042;
(b) Counterterrorism and Forensic Science Analysis Unit, Federal Bureau of Investigation
Laboratory Division, 2501 Investigation Parkway, Quantico, VA 22135;
(c) Latent Print Help Unit, Federal Bureau of Investigation Laboratory
Division, 2501 Investigation Parkway, Quantico, VA 22135

Edited by Stephen E. Fienberg, Carnegie Mellon College, Pittsburgh, PA, and accepted March 31, 2011 (acquired for evaluation December 16, 2010)

Proceedings of the Nationwide Academy of Sciences (PNAS)
April 25, 2011

The Numbers Behind Numb3rs: Fixing Crime with Arithmetic
Keith Devlin, Ph.D. and Gary Lorden, Ph.D.
Penguin Books, New York, 2007


The fingerprint picture is from Wikimedia Commons and is within the public area. Fingerprint Picture at Wikimedia Commons

In regards to the Writer

John F. McGowan, Ph.D. solves issues utilizing arithmetic and mathematical software program, together with creating video compression and speech recognition applied sciences. He has intensive expertise creating software program in C, C++, Visible Primary, Mathematica, MATLAB, and lots of different programming languages. He’s in all probability greatest recognized for his AVI Overview, an Web FAQ (Continuously Requested Questions) on the Microsoft AVI (Audio Video Interleave) file format. He has labored as a contractor at NASA Ames Analysis Middle concerned within the analysis and improvement of picture and video processing algorithms and know-how. He has printed articles on the origin and evolution of life, the exploration of Mars (anticipating the invention of methane on Mars), and low-cost entry to area. He has a Ph.D. in physics from the College of Illinois at Urbana-Champaign and a B.S. in physics from the California Institute of Expertise (Caltech). He might be reached at [email protected].