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In 2004, a train bombing in Madrid, Spain killed 193 and injured over 2,000. We now know that Al-Quada was behind this terrorist attack. But at the time, investigators went in a very different direction. The FBI quickly arrested Brandon Mayfield, a mild-mannered family law attorney in Oregon. Why did they do this? A fingerprint left on one of the detonators was considered a match with Brandon Mayfield’s fingerprint.

The Facts Don't Match Up

There were many problems with this theory that Brandon Mayfield was responsible. First among these was that Mayfield had not left the country in over ten years. He had no valid passport. He was of the Muslim faith. But he had no extreme beliefs. He had no ties to terroristic organizations. He was not violent. There was absolutely nothing connecting Mayfield to this crime. He verifiably wasn't even in the same hemisphere of the crime. The Spanish authorities never believed the FBI's theory that Mayfield was involved. The Spanish authorities correctly identified the prints as belonging to Ouhnane Daoud, an Algerian national and member of Al-Qaeda. Mayfield was released from prison and the FBI apologized to Mayfield. 

Isolated Incident or Pervasive Problem?

The error was not a small one. Three different trained fingerprint analysts claimed with 100% confidence that Mayfield’s print matched. Some of the revisionist history that the FBI have done in the aftermath is to pretend that the analysts just made errors in this particular case and that otherwise fingerprint analysis is still a solid forensic science. Nothing could be further from the truth. The problems with fingerprint analysis go straight to its core.

Human Judgment Masquerading as Science

It shocks most people when they are told fingerprint analysis is completely subjective. There is a reason why the National Academy of Sciences (NAS) was very critical with how fingerprint analysis has been used in the criminal justice system. (NAS, p. 92). Fingerprint analysis involves the use of the ACE-V method. ACE-V stands for: Analysis, Comparison, Evaluation, and Verification. The National Academy of Science quotes a scientist approvingly who said, “We have reviewed available scientific evidence of the validity of the ACE-V method and found none.” (NAS, p. 93). At its core, fingerprint analysis is just using human judgment and is not science.

Appearances are Not Always Reality


So, is this human judgment accurate? Fingerprint analysis was first introduced into courts over 100 years ago. It’s entrenched in solid evidence in the public consciousness. The image of a detective dusting for prints on movies and TV shows feels so precise and exacting. It’s got to be accurate, it looks that way on TV!

Claims of Accuracy: A History of Puffery

In 1984, The U.S. Department of Justice claimed that fingerprints analysis done correctly would have an error rate of “zero”. (President's Council of Advisors on Science and Technology 2016 report (PCAST), p. 87). With no sense of irony, they even went so far as to claim that fingerprint evidence was “infallible”. (PCAST, p. 87). Later, the FBI walked back that number to 1 in 11 million. (PCAST, p. 53). It wasn’t until after the Brandon Mayfield kerfuffle that the FBI went back and did more analysis. From this, the FBI claimed that the upper bound for false positives was 1 in 306 cases. (PCAST, p. 94). However, independent studies from agencies not connected with law enforcement found far greater error rates than what the FBI was claiming. Most notably, the Miami-Dade study of 2014 put the false positive rate at 1 in 18 cases. (PCAST, p. 96).

The walk back in claims about the accuracy of fingerprint analysis has been steeper than the walls of the Grand Canyon. Starting at infallible, going down to 1 in 11 million, and then hitting 1 in 18. It literally started at infinity and ended in double digits.

The Evidence is Still Treated as Flawless in Jury Trials

The most troubling thing for our criminal justice system is that when polled, jurors believe the error rate for fingerprint analysis is 1 in 5.5 million. (PCAST, p. 95). Which means jurors are overconfident about fingerprint analysis evidence to the tune of 305,555 times more confident than they should be. Which creates an absurd proposition for defendants accused of crimes who are supposed to be presumed innocent and only convicted beyond a reasonable doubt. The defendants are being measured with evidence that will falsely implicate them 1 out of 18 times, but measured against a measuring rod from a jury that thinks it only happens 1 in 5.5 million times. Under these circumstances, receiving a fair trial becomes difficult if not impossible.

Cases Get Charged That Never Should Have

Falsely accused people pay dearly for this problem. The Public Defender’s Office in LA County, California, have counted 25 false positives of fingerprint analysis for cases they have encountered in their office alone. Do you think LA County is remarkable with regard to charging so many people over fingerprint evidence that is that actually wrong? I don’t. The error rates suggests this is a pervasive problem. LA County is just unique in that they went to the trouble to quantify how frequently it was happening. Or at least how many times they have been able to prove it. The error rate on fingerprint analysis is much higher than what most people realize.

Takeaways for the Falsely Accused

If you are falsely accused over fingerprint evidence, a two prong attack will likely be needed. First, a motion to exclude the fingerprint analysis as evidence at trial and/or expert testimony. In theory, a judge should exclude or strictly limit the evidence that comes in because fingerprint analysis is not science and is deeply flawed. But you can’t rely on theory leading to reality. Courts notoriously let in fingerprint evidence and the Government’s expert testimony despite how precipitous the fall in claimed accuracy has been.


That’s why you will likely need to be prepared for prong two which is a full-blown attack on the fingerprint evidence at trial. The jury needs to know the full extent to which fingerprint evidence is just human judgment. The problem is that there are so many court rules that prevent a lawyer from just telling the jury what’s wrong with the evidence. That’s why you want a lawyer who’s skilled at crafting a strategy at trial to blow to pieces the Government’s argument that the fingerprint evidence proves guilt. It doesn’t. And sadly, many attorneys are unaware of how troubled fingerprint evidence is. So, getting an attorney who knows this issue is very important. You don’t want to be wrongfully convicted on fingerprint evidence.

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Peter Lindstrom, Esq.

Founder of Subzero Criminal Defense

I practice exclusively in the state of Minnesota. If you are falsely accused in Minnesota, contact me for a consultation. If you are falsely accused in another state or country, contact a qualified attorney in your jurisdiction. 

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