John Hay Biomedical • Original simulated practice

Chain of custody: track the evidence

PBS • Week 3 • September 8, 2026

Today, focus on chain of custody. If you already passed safety, do not retake the test. If you are new or have not passed, use the safety catch-up directions in Schoology. Ask me if you are unsure.

Your job

Check whether an evidence record accounts for an item's handling. Turn in one document with three parts: a four-record review, one transfer entry, and a two-sentence conclusion.

You need this handout and paper or a document you can type in. This is a paper-based practice. Do not handle chemicals or collect real biological samples.

Source label: All records below are original, AI-assisted simulated practice. The people, items, and events are fictional. These are not evidence from PLTW's Anna Garcia case. This practice supports the documentation skills in PLTW Activity 1.1.1, A Sketchy Scene. Use the official handout in Schoology for that activity.

1. Learn the rule

How can we check that the item tested is the item collected?

An observation is something recorded directly. An inference is an explanation drawn from observations. Keep them separate when you read a record.

Chain of custody is the record of an evidence item's collection, storage, and transfers. A transfer is a change in who is responsible for the item. An item ID is its unique label. A seal helps show whether a package has been opened. Condition describes the item's or package's state, such as dry, wet, sealed, or torn.

A transfer record identifies the item, date and time, sender, receiver, purpose, location, and condition. A signature or secure electronic receipt confirms the handoff. A signature alone does not tell us whether the package stayed sealed.

Check two things separately:

1. Record: Can you account for who had the item and when?
2. Condition: Is there a reported change that could affect the item?

Use these decisions: no gap shown, gap or concern shown, or not enough information. Name the fact behind your decision. Missing information does not prove that someone changed the evidence. Do not fill a gap with a guess.

Forensic teams use these records when they transfer samples for DNA testing. A lab result cannot supply a missing handling record. Your job today is to assess the record, not decide guilt or a cause of death.

2. Study one worked model

Model M: simulated blue thread

Practice case M. Collector M1 collected item M-1, a dry blue thread, from a chair at 9:00 AM on September 8, 2026. M1 labeled and sealed it in a paper packet. M1 kept it until the handoff below.

What to notice: The item ID stays the same. A new person becomes responsible at a recorded time.

Model decision: No gap is shown from collection to this handoff. The record names both people, the time, the item, and the intact seal. It does not tell us what happened after 9:15 AM.

Try the rule: If the receiver field were blank, what question would you ask before trusting the transfer record? Write one question in your notes.

3. Review four practice records

All four records are separate simulations dated September 8, 2026. Review only the interval described. Do not assume an unreported earlier or later event happened.

R1 • Sealed envelope. At 10:00 AM, collector A1 gave item R1-1 to technician A2 for storage in locker 3. The item label matched the record. Both signed at 10:00 AM and recorded an intact seal. A2 placed it in the locked locker immediately.

R2 • Unattended packet. Collector B1 left sealed item R2-1 on an open classroom table at 10:05 AM. B1 returned at 10:20 AM. No one was assigned to watch it. B1 recorded that the seal still looked intact. The record does not identify who had access during those 15 minutes.

R3 • Missing receipt. Collector C1 wrote, "Gave sealed item R3-1 to C2 at 10:30 AM for secure storage in locker 4." The receiving-confirmation field is blank. No secure electronic receipt is supplied. The record does not report a damaged seal.

R4 • Torn package. At 10:40 AM, D1 gave item R4-1 to D2 for storage in locker 5. Both signed. Their record says, "Package torn; opening exposes the dry thread inside." The record does not explain when the tear occurred or whether anything touched the thread.

Copy this table. Write a short answer in each cell.

Need a starting point? Ask who, when, and which item. Then look for a stated condition. A next step might confirm a receipt or report a documented problem. Do not invent a signature or silently rewrite an earlier entry.

4. Make one transfer entry

Record T • Simulated paper sample. Practice case T. E1 collected item T-1, a dry paper square, from practice station 2 at 11:00 AM. E1 labeled and sealed it, then kept it until 11:12 AM. At 11:12 AM on September 8, 2026, E1 handed it to E2 for secure storage in locker 6. Both checked the item label and intact seal. Both signed at the handoff.

Use the Model M field names to write this transfer entry. Include all six rows. Write the supplied confirmation fact; do not imitate anyone's signature.

5. Finish and turn in

Write two sentences about R2, R3, or R4:

1. "Record ___ shows ___ because ___."
2. "It does not show ___, so my next step is ___."

Check that your document contains the four-row review, the six-field transfer entry, and both sentences. Submit it to your section's Week 3 chain-of-custody assignment in Schoology. Check that assignment for the deadline.

Remember: Record what you know. Mark what you do not know. Never repair a gap by inventing a fact.

Next lesson: Apply careful documentation to the PLTW scene work. Keep today's practice records separate from the official case file.

Optional source reading

The required facts are in this handout. These National Institute of Justice training pages explain the professional practices behind it:

• Chain of Custody, 2023.
• Documentation: Chain of Custody, accessed September 5, 2026.
• Preservation of Evidence, 2023.