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Chain of Custody Flow

Run the Chain of Custody Flow Fullscreen

About This MicroSim

The chain of custody is the documented, unbroken trail showing who handled a piece of evidence, when, and what they did with it — from the moment it is collected at a crime scene to the moment it is presented in court. If any link in that chain is missing, the defense can argue the evidence was lost, swapped, or tampered with, and a judge may rule it inadmissible.

This MicroSim lets you step through the journey of a single evidence item across six custody stations. At each step you see who is responsible, what gets recorded (item ID, date, location, condition notes, and a signature), and what would go wrong if that step were skipped. The Break the Chain toggle removes a signature at the step you are on so you can see exactly how — and why — a single gap can sink an entire case.

How to Use It

  1. Press Next > to advance the evidence item to the next custody station. Press < Prev to step back.
  2. Read the detail panel at the bottom: it names the responsible person, the form fields recorded, and the transfer signature for that station.
  3. Watch the track at the top. Completed transfers turn green ("signed"); the station you are on is highlighted in blue (or gray for secure storage).
  4. Tick Break the Chain to drop the signature at your current step. A red X marks the broken link and an EVIDENCE INADMISSIBLE banner explains the legal consequence.
  5. Uncheck the box to restore the link, or press Reset to start over at the crime scene.

What You Can Learn

  • Explain the six stages an evidence item passes through, from collection to courtroom presentation.
  • Identify the documentation required at each transfer: item ID, date and time, location, condition notes, and a custodian signature.
  • Describe how a tamper-evident seal and a continuous signature record protect evidence against contamination and substitution.
  • Reason about why a single missing signature can make otherwise solid evidence inadmissible — connecting procedure to courtroom admissibility.

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

<iframe src="https://dmccreary.github.io/forensic-science/sims/chain-of-custody-flow/main.html"
        width="100%" height="562" scrolling="no"></iframe>

Lesson Plan

Audience: High-school forensic science (grades 9–12) Time: 15–20 minutes Bloom level: Understand (L2) — explain the chain of custody and the documentation required at each transfer.

Step-and-explain (the core routine). Have students advance one station at a time and, before reading the panel, say out loud who they think is responsible and what should be recorded. They then check their explanation against the panel. The goal is for students to be able to narrate the full chain in their own words, which is exactly what an Understand-level objective asks for.

Guided questions:

  • Name the two stations where the evidence item is sealed (or re-sealed), and explain why a fresh seal matters after laboratory testing.
  • The custodian logs the item into the property-management system at the evidence room. What four pieces of information are recorded there?
  • Use Break the Chain at the Supervisor Review step. In one sentence, explain to a jury why that gap is a problem — even if the lab results are perfect.

Extension. Ask students to write a short courtroom exchange in which a defense attorney challenges a piece of evidence based on one broken link, and the prosecutor responds using the chain-of-custody record. Note honestly that even a complete chain does not guarantee the scientific conclusion is correct — it only shows the item was not altered.

References

Specification

This MicroSim was generated from a specification in Chapter 2: Crime Scene Investigation and Evidence Collection.

Design note: the specification described click-to-open station panels, an arrow-hover detail, and a free-form "Break the Chain" click mode. Because the learning objective is at the Understand (L2) level — explain the chain — the interaction was implemented as a guided step-through (Next / Prev) with a single always-visible detail panel, rather than continuous animation or free exploration. This keeps the concrete data (who, what, signature) visible at every step and makes the workflow easy to narrate. The Break the Chain idea is preserved as a checkbox that drops the signature at the current step, so students still see the red broken link and the INADMISSIBLE consequence in context.