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Fingerprint Analysis Not as Certain as Prosecutors Want You to Believe

We’ve all seen cop shows and the courtroom dramas where the alleged criminal is identified by a fingerprint found somewhere in the crime scene. That fictional drama happens in real life in Kentucky every day, but the reality is that the science of determining who matches a latent fingerprint may be far more uncertain than what you might believe.

Courtroom testimony and reports claiming or even implying fingerprints collected from a crime scene belong to a single person are indefensible and lack scientific foundation, according to an American Association for the Advancement of Science (AAAS) working group report on the quality of latent fingerprint analysis published last year.

Latent fingerprints are concealed impressions left by an unknown person and made visible by use of lasers or powders, often as part of crime investigations. Crime scene investigators lift the impressions from their surface. Fingerprint examiners analyze a fingerprint by comparing it against others in an effort to find similarities and make judgments about common traits.

The report states that latent print examiners should not claim they can associate a latent print with a single person and should also avoid claiming or implying that they can do so with perfect accuracy. Forensic examiners claimed for many years that their decisions were made with high levels of certainty that fingerprints came from a specific person. Scientific studies have shown that’s not the case.

Studies by the National Research Council in 2009, a National Institute of Standards and Technology’s working group on latent fingerprint analysis in 2012, and, most recently, the President’s Council of Advisors on Science and Technology in 2016, reached similar conclusions. Claims of accuracy have been shown to have led to false arrests and convictions.

Most fingerprint examiners no longer claim perfect accuracy. They have soft pedaled and claim they can “identify” or are “practically certain of” the source of a latent print. The AAAS report states there’s no scientific basis for either claim.

What can be done, according to the report, is to exclude most of the population as being the source of a latent fingerprint based on features of the fingerprint. There is currently not enough data to decide how unique fingerprint features really are, so there’s no scientific basis to claim that examining latent fingerprints can result in narrowing the pool of possible sources to a single person.

The AAAS report states that without estimates of the accuracy rates of examiners, testimony by examiners that two fingerprints are the same is scientifically meaningless and shouldn’t be allowed as evidence in court. Any belief by latent print examiners that they can narrow down the possible source to one person is based on speculation and guesswork, not objective, empirical evidence.

Issues that researchers considered included:

  • – Studies on the differences in human fingerprints
  • – The differences of a fingerprint lifted at different points in time, from different fingers or hands, or under a variety of conditions
  • – The accuracy of automated fingerprint systems
  • – How subjective judgments by latent fingerprint examiners can influence their findings, including when they are given information about a criminal investigation or shown an existing fingerprint of a suspect
  • – The accuracy rates of fingerprint examiners.

Criminal defense is much more than dramatic, courtroom confrontations that you see on TV. It often boils down to tiny, but critical, pieces of evidence that can be disputed by highly qualified, scientific experts. How well a defense expert does his or her job and how well the person testifies at trial could be the difference between a guilty verdict and the release of a defendant from custody.

If you live in Kentucky and are being investigated by law enforcement or have been charged with a crime, fill out our contact form or call us at (859) 971-0060 so we can discuss the criminal legal process, applicable laws and how we can help defend your liberty, your future and your ability to support your family.