Collect and analyze evidence
Collect and analyze evidence from a mock crime scene using observation, fingerprint dusting with safe materials, measurements, and logical reasoning to identify the culprit.
About this activity
Collect and analyze evidence from a mock crime scene using observation, fingerprint dusting with safe materials, measurements, and logical reasoning to identify the culprit.
What you need
Step by step
- 1
Step 1
Gather all the Materials Needed and bring them to a small table or tray.
- 2
Step 2
Clear the table area so you have a clean space to make your mock crime scene.
- 3
Step 3
Place the 3 small objects around the table to create the mock crime scene.
- 4
Step 4
Look carefully at the scene and draw a simple map in your notebook showing where each object is.
- 5
Step 5
Measure the distances between the objects with the ruler and write the numbers on your map.
- 6
Step 6
Put a small pinch of cocoa powder on a paper plate to use for fingerprint dusting.
- 7
Step 7
Gently dip the soft brush into the cocoa and lightly brush the surface of the first object to reveal any fingerprints.
- 8
Step 8
Press a small piece of clear tape gently onto the powdered fingerprint to lift it.
- 9
Step 9
Stick the lifted tape onto a piece of white paper to preserve the fingerprint.
- 10
Step 10
Repeat Steps 7 to 9 for the other objects to preserve each fingerprint.
- 11
Step 11
Ask three family members to each make a sample fingerprint by lightly touching cocoa on the plate then pressing their fingertip onto white paper.
- 12
Step 12
Write each sample maker’s name on the back of their paper so you know who is who.
- 13
Step 13
Use the magnifying glass to compare the preserved fingerprints to the sample prints and look for matching ridge patterns.
- 14
Step 14
Decide which sample best matches the evidence using your comparisons and measurements and write your conclusion in the notebook.
- 15
Step 15
Share your finished investigation on DIY.org.
Fun facts
How do you collect and analyze evidence at a mock crime scene?
Set up a small mock crime scene with a defined area and staged clues (spilled beads, broken vase, toy footprints). Have the child first observe and sketch the scene, take photos, and note measurements. Use a soft brush and a safe powder (cocoa or baby powder) to dust for fingerprints, then lift prints with clear tape onto cardstock. Record each item on an evidence sheet, compare prints/suspect statements, and use logical reasoning to identify the culprit under adult supervision.
What materials do I need for a mock crime-scene activity?
You'll need: a small area or tray to create the scene, props (toys, fake breakable object), camera or smartphone, ruler/tape measure, clipboard and evidence sheets, pencil, magnifying glass, soft paintbrush, non-toxic dusting powder (cocoa, cornstarch, or baby powder), clear tape to lift prints, index cards or envelopes for evidence, disposable gloves, zip-top bags, a washable ink pad (optional), and adult supervision.
What ages is this mock crime-scene activity suitable for?
This activity suits children about 6–14. Younger kids (6–8) enjoy observing, sketching, and simple evidence collection with close supervision and non-messy dusting alternatives like washable ink or printable fingerprint sheets. Ages 9–11 can handle more detailed measurements, tape lifts, and comparing prints with guidance. Tweens 12–14 can apply logical reasoning, document chain of custody, and lead the investigation. Adapt complexity and tools to each child’s maturity and motor skills.
What safety precautions should I follow for this activity?
Safety first: supervise closely. Use only non-toxic, food-grade powders (cocoa, cornstarch) or washable ink. Avoid fine dusts that can be inhaled; work in a well-ventilated area and keep faces away from powders. Keep small evidence and tape away from toddlers to prevent choking. Wear gloves if desired, wash hands after, and protect surfaces with newspaper. Explain proper handling of evidence and never use real chemicals or sharp tools; choose alternatives if anyone has allergies.
Watch & Learn
Need help?
My family doesn't have cocoa powder, a soft brush, or a magnifying glass—what safe substitutes can we use for Step 5 and Steps 7–11?
Use cornstarch or talc‑free baby powder instead of cocoa for Step 5, a clean soft paintbrush or makeup brush for Step 7, and a smartphone camera with zoom or reading glasses in place of the magnifying glass for Step 11.
If I brush and don't see any fingerprints or the tape won't lift them, what should I try?
Use very light strokes with the soft brush and less cocoa in Step 7, press the clear tape gently and lift at an angle in Step 8, and if prints still fail check that the object surface isn't oily or try a finer powder before repeating Steps 7–9.
How can I adapt the activity for a 4-year-old, an 8-year-old, and a 12-year-old?
For a 4-year-old simplify Steps 4–6 by having them place and count stickers on a prearranged scene, for an 8-year-old let them dust and lift prints with supervision in Steps 7–9 and compare with the magnifying glass in Step 11, and for a 12-year-old have them take precise measurements with the ruler in Step 6 and write a detailed conclusion in Step 12.
How can we make the investigation more advanced or personalized before sharing it on DIY.org?
Enhance the activity by photographing each object with a ruler scale after Step 6, labeling each lifted print on the white paper from Step 9 with the sample maker's name from Step 10, and adding a typed report of your measurements and match from Step 12 to upload in Step 13.