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AFIS Search Workflow

Run the AFIS Search Workflow MicroSim Fullscreen

About This MicroSim

The Automated Fingerprint Identification System (AFIS) does not "match" fingerprints by looking at pictures. It converts a print into a list of numbers — the locations and angles of minutiae (ridge endings and bifurcations) — and compares that numeric template against millions of stored templates. The crucial point for investigators: AFIS produces a ranked list of candidates, not an identification. A trained human examiner always makes the final call.

This MicroSim walks through the five stations of that pipeline, with concrete data shown at each step: the scanned print, the extracted (x, y, angle) template, the database search, the scored candidate list, and the examiner review.

How to Use It

  1. Use Next ▶ and ◀ Prev, or click any station box, to move through the five stages.
  2. At Minutiae Extraction, watch the red (ridge-ending) and blue (bifurcation) dots appear one by one as the encoded coordinate list fills in. Press Replay animation to run it again.
  3. At Candidate List, read the AFIS similarity scores (92, 78, 61 out of 100) — note that a high score is a lead, not a conclusion.
  4. At Examiner Review, read the banner: AFIS never makes the identification on its own.

What You Can Learn

  • Explain how AFIS encodes a fingerprint as a numeric minutiae template rather than as an image.
  • Describe what an AFIS candidate list and its scores actually mean.
  • Explain why the human examiner — not the computer — makes the final identification or exclusion.

You can embed this MicroSim on your own web page with this iframe:

<iframe src="https://dmccreary.github.io/forensic-science/sims/afis-search-workflow/main.html"
        width="100%" height="507" scrolling="no"></iframe>

Lesson Plan

Audience: High-school forensic science (grades 9–12) Time: 15–20 minutes Bloom level: Understand (L2) — explain the AFIS pipeline.

Walk-through. Step through the five stations as a class. At Stage 2, pause to discuss why a numeric template (not the photo) is what gets searched. At Stage 5, discuss why the law treats AFIS output as investigative, not conclusive.

Guided questions:

  • What two kinds of minutiae does AFIS encode, and what does each (x, y, angle) value describe?
  • A candidate scores 92/100. Has the person been identified? Why or why not?
  • Why is the final station colored green instead of blue?

Extension. Have students research a real case where an AFIS candidate was later excluded by a human examiner, and discuss the consequences of treating a high score as proof.

References

Specification

This MicroSim was generated from a specification in Chapter 3: Fingerprint Analysis and Dactyloscopy.

Design note: the fingerprint images are stylized loop-pattern drawings and the minutiae coordinates, database count, and candidate scores are illustrative values chosen to teach the workflow, not output from a real AFIS system.