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Minutiae-Tagging Canvas

Run the Minutiae-Tagging Canvas Fullscreen

About This MicroSim

An Automated Fingerprint Identification System (AFIS) does not compare pictures of prints. It reduces each print to a map of minutiae — the coordinates and types of every ridge ending and bifurcation — then looks for database records whose maps overlap the crime-scene map and scores each one. The output is a ranked candidate list, not a "guilty" stamp.

This MicroSim lets investigators generate that map by hand. You tag the minutiae on a stylized loop print, and each tag is scored against a hidden ground-truth set. When you search the database, the six suspects are ranked by how many of your correctly tagged minutiae they share. The point is built into the design: AFIS ranks candidates, and a human examiner — not the computer — makes the final identification.

How to Use It

  1. Pick a Tag type from the dropdown — Ridge ending (drawn as a circle) or Bifurcation (drawn as a triangle).
  2. Click on the print to place a tag on each minutia you find. Each tag turns green (correct spot and type), orange (right spot, wrong type), or red (off-ridge — no minutia there).
  3. Press Search AFIS Database to rank all six suspects by how many of your correctly tagged minutiae overlap each one's template. Read the ranked list and the score bars on the right.
  4. Use Show Answer to reveal the ground-truth minutiae as dashed markers and check your tagging.
  5. Press Clear Tags to start over and try to place all six.

Learning Objective

Locate and classify minutiae on a latent print and interpret the resulting ranked AFIS candidate list, recognizing that the system ranks while a human examiner decides (Bloom Level 4 — Analyze).

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

<iframe src="https://dmccreary.github.io/forensic-science/sims/minutiae-tagging-canvas/main.html"
        width="100%" height="560" scrolling="no"></iframe>

Lesson Plan

Audience: High-school forensic science (grades 9–12) Time: 15–20 minutes Bloom level: Analyze (L4) — locate and classify minutiae and interpret a ranked candidate list.

Warm-up. Show investigators a loop print and ask: "A computer cannot really 'see' a fingerprint the way you do. What handful of features could you reduce this print to so a database could compare it quickly?"

Guided questions:

  • Tag several minutiae and read the green, orange, and red feedback. What is the difference between a ridge ending and a bifurcation, and why does getting the type right matter to AFIS?
  • After you search the database, the six suspects come back ranked. Why does AFIS return a ranked candidate list instead of a single "match"?
  • Whose job is it to make the final identification — the computer or a human examiner — and what could go wrong if we skipped the human step?

Extension. Research how real AFIS systems weight minutiae direction and ridge count, and discuss why a high score is a lead to investigate, not proof of identity.

References

Specification

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

Design note: the print, ground-truth minutiae, and six-suspect database are stylized for teaching — scoring rewards correct location and type qualitatively rather than reproducing a production AFIS matching algorithm.