Skip to content

Fiber Identification Decision Tree

Run the Fiber Identification Decision Tree MicroSim Fullscreen

About This MicroSim

A forensic analyst rarely identifies a fiber from a single test. Instead they follow a protocol — a burn test first, then microscopy, then a solubility test — and each result narrows the possibilities. This MicroSim turns that protocol into a decision tree you walk one choice at a time.

Each new sample is an unknown fiber with a fixed set of observed test results shown on the right. Your job is to read those observations and answer Yes or No at each yellow decision diamond, following the branch your answer selects until you reach a leaf — the fiber's classification.

How to Use It

  1. Read the Unknown Sample card: its burn behavior, microscopic cross-section, and (for some fibers) solubility result.
  2. Look at the highlighted decision diamond and its full question.
  3. Press Answer: Yes or Answer: No based on the sample's observed result. The branch you choose lights up green and the next node highlights.
  4. Reach a leaf to see the classification. A green check (✓) means your path matched the sample; a red ✗ means a step diverged — trace back to find where.
  5. Press Start New Sample to get a different unknown fiber.

What You Can Learn

  • Apply a sequential identification protocol instead of guessing from one test.
  • Use burn behavior to split natural fibers (which char and smell of paper or hair) from synthetic fibers (which melt and form a hard bead).
  • Distinguish protein fibers (wool, silk) from cellulosic (cotton), and polyester from nylon, using the later branches.

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

<iframe src="https://dmccreary.github.io/forensic-science/sims/fiber-identification-tree/main.html"
        width="100%" height="532" scrolling="no"></iframe>

Lesson Plan

Audience: High-school forensic science (grades 9–12) Time: 20–25 minutes Bloom level: Apply (L3) — apply.

Worked example. Start a sample and read its results aloud as a class. Predict the final classification before walking the tree, then traverse it together to confirm. Discuss which single test was most decisive.

Guided questions:

  • The very first decision asks whether the fiber melts. Why is "melts vs. burns" such a powerful first split?
  • A sample smells like burning hair and leaves a crushable bead. Which two fibers are still possible, and what test separates them?
  • What is the difference in the burn residue between nylon and polyester?

Extension. Deliberately answer one decision wrong and follow it to the incorrect leaf. Explain in your own words where the logic diverged and why the classification is wrong.

References

Specification

This MicroSim was generated from a specification in Chapter 4: Hair, Fiber, and Trace Evidence Analysis.

Design note: the five fibers, their observed test results, and the branching logic are a simplified teaching model of a real identification protocol — actual casework uses additional instruments (FTIR, polarized-light microscopy) and more fiber types. Per the build guidelines, the Yes/No choice at each node is made with native p5 buttons rather than by clicking the diamond directly; the highlighted diamond shows which node the buttons act on.