Did You Know?

I've watched so many mystery stories on T.V, when I turn off the set I wipe my finger-prints off the remote. (Anonymous)


Fingerprint Analysis: Problems & Guidance

A fingerprint is an impression left on the surface of some material (desk, cloth, body, glass, paint, etc.) made by the friction ridges of all or any part of the finger, palm, foot or toes. A friction ridge is a raised portion of the epidermis (skin on the finger, foot, palm or toe) from the palmar (palm and fingers) or plantar (sole of foot and toes) skin, comprised of one or more joined ridge units of friction ridge skin, also known as dermal ridges or dermal papillae.

Fingerprint identification (dactyloscopy) is the process of examining and analyzing questioned and known friction skin ridge impressions(fingerprints, palm prints, footprints, and toe prints)  to determine if the impressions are from the same finger or palm, toe, in order to attempt to determine the probability (statistical outcome... i.e. 1 in 100,000) that the person who left the prints is the same person from whom the known examples were connected.

The flexibility of friction ridge skin has been presumed to mean that no two finger or palm prints are ever exactly alike, therefore the identification of an individual is assured when examination occurs matching prints to known exemplars to suspects. Historically, fingerprint identification (individualization) occurred when a criminal justice or other expert or an expert computer system operating an identification system and using threshold scoring rules, determined that two friction ridge impressions originated from the same finger or palm ( toe, sole) to the exclusion of all others (all other known persons) and therefore identified a particular/unique person.

For more than a century, fingerprints, palm prints, and sole prints have been used as identification tools by US law enforcement to assert the linkages of dactyloscopy to connect crimes to criminals. Friction ridge analysis involves trained examiners comparing details of an unknown print with a set or a database of known prints, such as those collected and stored by local law enforcement, state bureaus of investigation and of course, the FBI. Print details include ridges, loops, whorls and other points of similarities used to express the minutia (the tiny detail) of ridge configurations and traits. Moreover, criminologists and law enforcement officials have relied upon the assumption that fingerprint identification was flawless and foolproof.

In print identification both the collection and examination are key to the accuracy and correct identification of a suspect to an offense. Poor or inaccurate collection and identification processes create risk to victims when suspects are not identified and innocent suspects being wrongfully charge or worse, convicted of crimes they did not commit. The International Association of Identification provides for strict certification standards for examiners.


Latent print identification relies on three levels of detail

Level 1 detail -- Ridge flow (patterns)
Level 2 detail -- Ridge formations (ridge endings, bifurcations, dots, or combinations)
Level 3 detail -- Ridge path deviation (ridge structure or formation, which includes ridge width, shape, pores and other minutiae)

Improved Procedures

  • Analysis – the qualitative and quantitative assessment of Level 1, 2, and 3 details to determine their quantity, interrelationship and significance to individualize.
  • Comparison – to examine the trait observed during analysis in order to determine agreement or inconsistencies between two friction ridge impressions.
  • Evaluation – the repeated procedure of comparison between two friction ridge impressions to effect a decision, in other words, those  made by the same friction skin, not made by the same friction skin, or inadequate detail to form a conclusive evaluation.
  • Verification – an independent analysis, assessment and evaluation by another qualified examiner of the friction ridge impressions. 

Unfortunately, errors and laboratory mismanagement at state and federal levels added fuel to the fire about the reliability of fingerprint forensic evidence. A number of famous cases of misidentification by examiners and the fingerprint evidence they analyzed. As of 2012, the National Academies of Sciences has indicated that no peer reviewed scientific studies (research, facts, data) has ever been done to prove or disprove the basic assumption that every person’s fingerprint is unique. Moreover, research has shown that fingerprint examiners can be influenced by contextual bias (interpretation of information based on preference or bias) when comparing fingerprints.

Famous cases involving problems with fingerprint examination include:

The Case of Shirley McKie  www.clpex.com/McKie.htm

The Case of Riky Jackson    articles.latimes.com/2002/feb/26/news/mn-29922

The Brandon Mayfield Case   www.justice.gov/oig/special/s0601/PDF_list.htm

As a result of those cases and others less well known to the public, the National Institute of Standards and Technology (NIST) established recommendations and policies to be applied in forensic latent print analysis  to reduce the risk of error. A brief of that report and link to those recommendations follows below,

Title: Latent Print Examination and Human Factors: Improving the Practice through a Systems Approach
Published: February 17, 2012
Abstract: Fingerprints have provided a valuable method of personal identification in forensic science and criminal investigations for more than 100 years. The examination of fingerprints left at crime scenes, generally referred to as latent prints, consists of a series of steps involving a comparison of the latent print to a known (or exemplar) print. In addition to reaching correct conclusions in the matching process, latent print examiners are expected to produce records of the examination and, in some cases, to present their conclusions and the reasoning behind them in the courtroom. In recent years, the accuracy of latent print identification has been the subject of increased study, scrutiny, and commentary in the legal system and the forensic science literature. In December 2008, the U.S. National Institute of Standards and Technology (NIST) convened The Expert Working Group on Human Factors in Latent Print Analysis to conduct a scientific assessment of the effects of human factors on forensic latent print analysis and to develop recommendations to reduce the risk of error. This report documents their findings and recommendations, addressing issues ranging from the acquisition of impressions of friction ridge skin to courtroom testimony, from laboratory design and equipment to research into emerging methods for associating latent prints with exemplars. It provides a comprehensive discussion of how human factors relate to all aspects of latent print examinations including communicating conclusions to all relevant parties through reports and testimony.www.nist.gov/customcf/get_pdf.cfm

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