Detective Briefing Teacher Guide Detective Briefing
Lesson Plan: The Cookie Jar Detectives
GRADE 4 • ELA
Learning Objective
Students will be able to define "inference" and use specific evidence combined with background knowledge to draw logical conclusions from visual and physical clues.
Key Vocabulary
Inference Evidence Background Knowledge Logical Reasoning
Equipment List
"Cookie Jar Detectives" Slides
Case Report Worksheets
4-6 Brown Paper Bags
Prop sets for "Evidence Bags"
Instructional Sequence
00-05
The Hook: The Muddy Footprint
Display Slide 2
Ask: "Who made this footprint? How do you know?" Prompt students to move beyond "a person" to "someone wearing boots" or "someone who was just outside." Introduce the idea that we are combining clues with what we know .
05-15
Case Study: The Cookie Jar Mystery
Display Slides 3-6 (includes Khan Academy Video)
Watch the video. CRITICAL PAUSE at 1:17: Ask students to vote on who took the cookies based only on the trail of crumbs. Resume to reveal the inference about the heavy lid. Explain the formula: Evidence + Background Knowledge = Inference .
15-35
Field Work: Evidence Bags
Student Activity
Distribute Evidence Bags to groups. Students examine objects to infer where the owner went. They must record the specific object (Evidence) and why it matters (Background Knowledge) on their Case Report.
35-45
Debrief: Solving the Cases
Groups share their findings. Focus discussion on *how* they knew. (e.g., "I saw a shell, and I know shells are found at the beach, so I infer the owner went to the beach.")
Evidence Bag Setup Guide
Prepare 4-6 brown bags with the following sets of props. Use the "Evidence Labels" material to mark each bag.
BAG A The Beach Traveler
• Small bottle of sunscreen
• A seashell
• Sunglasses
Inference: Someone went to the beach.
BAG B The Master Chef
• A whisk or spatula
• An empty sprinkle container
• An apron (or oven mitt)
Inference: Someone was baking/cooking.
BAG C The Artist
• A paintbrush
• A dried-up palette or sponge
• Smudged pencil sketch
Inference: Someone was painting/drawing.
BAG D The Winter Explorer
• A wool mitten
• An empty packet of hot cocoa
• A small knit hat
Inference: Someone was out in the cold/snow.
Teacher Tip: Scaffolding Inferences
If students struggle, use the "If/Then" sentence starter:
"If I see [Evidence], and I know [Background Knowledge], then I can infer [Inference]."
Example: "If I see a mitten , and I know people wear mittens when it's cold , then I can infer this person went somewhere snowy ."
Detective Briefing Slides The Cookie Jar Detectives
Mission: Master the Art of Inference
FILE #04-ELA
STEP 1
The Hook
👣
EVIDENCE CLUE #1
Investigate:
Who made this footprint? How do you know?
Think about:
What kind of shoe was it?
Where was the person just now?
What was the weather like?
What is an Inference?
Clues (Evidence)
Background Knowledge
=
Inference
"It's not really a guess... it's filling in the gaps with what you already know."
Case Study: The Cookie Jar
DURATION: 05:00
Embedded media
Pause the Case!
Wait! Before the narrator solves it...
Who took the cookies?
Evidence 🔎
Trail of crumbs to the mouse hole.
Background Knowledge 🧠
How strong are mice? How heavy is the lid?
Vote Now: Mouse or Imposter?
Your Mission
Evidence Bag Field Work
1
Examine the contents of your Evidence Bag.
2
Record what you see (The Clues ).
3
Think about what you already know.
Final Report
Where did the owner of this bag go?
Detective Case Report Worksheet Top Secret
Case Report: The Evidence Bags
Detective Name:
Date:
Briefing I: The Muddy Footprint
Based on the image on the screen, record your first inference.
My Inference (What I think happened):
My Evidence (How I knew):
Briefing II: The Field Bags
Examine the objects in your assigned bag. Connect them to what you already know.
Bag
The Evidence (I see...)
Background Knowledge (I know...)
The Inference
Conclusion:
Conclusion:
Case Summary: Why is background knowledge just as important as the evidence? Evidence Bag Labels Evidence Bag Labels
Teacher: Cut along the dashed lines and tape these to your brown paper bags.
State Bureau of Investigation
Case File Number
A
Evidence Category: Personal Effects
Date of Collection: 01 / 19 / 2026
State Bureau of Investigation
Case File Number
B
Evidence Category: Personal Effects
Date of Collection: 01 / 19 / 2026
State Bureau of Investigation
Case File Number
C
Evidence Category: Personal Effects
Date of Collection: 01 / 19 / 2026
State Bureau of Investigation
Case File Number
D
Evidence Category: Personal Effects
Date of Collection: 01 / 19 / 2026
CAUTION: EVIDENCE BAG • DO NOT TAMPER • EVIDENCE BAG • DO NOT TAMPER • EVIDENCE BAG • DO NOT TAMPER • EVIDENCE BAG • DO NOT TAMPER • EVIDENCE BAG • DO NOT TAMPER
