Extending Use of the Extended Feature Set
Written by Melissa Taylor   


Latent print interoperability—the ability of a law enforcement agency to compare a latent fingerprint or palm print to images stored in automated fingerprint identification systems (AFIS) in other jurisdictions—is extremely limited today. Law enforcement agencies from local to international levels would all benefit from interoperability, a need specifically addressed in the National Academy of Sciences’ 2009 report, Strengthening Forensic Science in the United States: A Path Forward.

A major step toward interoperability was the incorporation of the Extended Feature Set (EFS) into the ANSI/NIST-ITL standard Data Format for the Interchange of Fingerprint, Facial and Other Biometric Information, also referred to as ANSI/NIST-ITL 1-2011, NIST Special Publication 500-290. This standard is available at: www.nist.gov/itl/iad/ig/ansi_standard.cfm

The latent print examiner community and all major AFIS vendors worked with the National Institute of Standards and Technology (NIST) to create the EFS. The EFS is designed to be used for vendor-neutral AFIS searches and for the interchange of latent print annotations among examiners as part of non-AFIS casework.

The Federal Bureau of Investigation’s Biometric Center of Excellence and NIST, in collaboration with the nonprofit research corporation, Noblis, have developed the EFS Training Tool, an interactive guide to train latent print examiners on the EFS, how to mark up friction ridge images using the standardized EFS encodings, and the EFS search profiles. The EFS Training Tool’s objectives are to:

  • Further the use of EFS, a common markup method for the latent print community.
  • Foster greater consistency in latent print markups for AFIS and for case work annotation.
  • Provide interactive markup training that is independent of proprietary AFIS rules.
  • Present a range of fingerprint image clarity and difficulty levels to provide growth opportunities, even for experienced examiners.

The training tool focuses on the most-used features in the EFS and each section includes interactive exercises, allowing examiners the opportunity to perform feature markups and compare them with examples marked by experts. Each exercise begins with less complex images and gradually increases in difficulty. The Training Tool addresses the following EFS features:

  • Region of interest
  • Orientation
  • Pattern classification
  • Cores
  • Deltas
  • Minutiae
  • Ridge quality map
  • Dots and incipients
  • Distinctive features
  • Center point of reference
  • Core-delta ridge counts
  • Ridge flow map

The Training Tool also describes how features are grouped to create EFS Search Profiles for AFIS searches. Each search profile—e.g., Image-Only, Minimal Markup, Quick Minutiae Search, and Detailed Markup Profile—requires different levels of examiner effort and allows the examiner to appropriately choose trade-offs between search accuracy and markup time.

The final section of the tool is a self-evaluation where the examiner practices performing several types of markup on single images and again compares his or her work against an expert’s. A reference section points to sources providing additional information related to friction ridge feature markup, interoperability, and relevant standards.

Navigation through this tool is flexible, intuitive, and user-driven. Because scoring is included for most features, an examiner can repeat the exercises to gain greater proficiency. The EFS Training Tool is available free to the latent community via the Web. It operates on most up-to-date browsers, including Internet Explorer (9 and 10), Chrome (latest version), and Firefox (7.0.1 and above).

The tool is available at: www.nist.gov/forensics/EFSTrainingTool/

Additional resources on latent interoperability are available on the NISt Forensic Sciences website at: www.nist.gov/forensics/publications.cfm

About the Author

Melissa Taylor is a management and program analyst with the Office of Special Programs at the U.S. Department of Commerce’s National Institute of Standards and Technology. Her work focuses primarily on fingerprint-related research and integrating human-factors principles into forensic sciences. Taylor currently serves as a member of the INTERPOL AFIS Expert Working Group, associate member of the IAI, and co-chair of White House Subcommittee on Forensic Science’s Latent Print AFIS Interoperability Task Force.

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