Evidence, Inference, or Assumption? Reading a Case File
- Grade band
- 7
- Duration
- 45 minutes
- Skill
- Distinguishing evidence, inference, and assumption
- Standards
- RI.7.1 — Cite several pieces of textual evidence to support analysis of what the text says explicitly as well as inferences drawn from the text.
- Materials
- Case file and student worksheet (printable, included)
- Statement sort cards (printable, included)
- Highlighters in two colors
Learning objectives
- Students will be able to distinguish a statement the text says explicitly (evidence) from a conclusion the text supports (inference) and a conclusion it does not support (assumption).
- Students will be able to cite several specific details from a text to support an inference.
- Students will be able to evaluate a suspect's alibi by judging whether the cited evidence is strong enough to support the conclusion drawn from it.
Lesson procedure
- Hook (5 minutes) — I Do. Walk in carrying a wet umbrella (or describe doing so). Ask: “What do you know? What can you infer? What might you be assuming?” Sort the class's answers on the board: it's wet (evidence), it's probably raining outside (inference), I walked here from home (assumption — nothing shows that).
- Define the three terms (5 minutes) — I Do. Evidence: what the text actually states. Inference: a conclusion the evidence supports, even though the text doesn't say it. Assumption: a conclusion that goes beyond the evidence or ignores evidence against it. Stress that an assumption can turn out to be true — it's still an assumption if the text doesn't support it.
- Read the case file (8 minutes) — We Do. Read “The Case of the Missing Trophy” aloud while students highlight facts in one color and anything they are tempted to conclude in a second color.
- Statement sort (10 minutes) — We Do / You Do. In pairs, students sort the ten statement cards into Evidence, Inference, and Assumption. For every inference card, they must name the line(s) in the case file that support it. Review with the smartboard sort.
- Written analysis (12 minutes) — You Do. Students complete Part 2, citing at least three pieces of evidence from the case file.
- Debrief (5 minutes) — Closure. Ask: “Which suspect did you want to blame first? What made you change your mind — or not?” Point out how often the most obvious suspect rests on an assumption.
Printable worksheet
Part 1: Read the case file. Highlight facts in one color. Highlight anything you're tempted to conclude in another.
The Case of the Missing Trophy
Friday, 3:30 p.m. The custodian, Mr. Patel, reports that the science fair trophy is missing from the glass display case in Room 12. He says the trophy was in the case when he locked Room 12's hallway door at 3:00 p.m.
Right after locking the door, Mr. Patel mopped the hallway outside Room 12. He says the floor stayed wet until about 3:20 and that there are no footprints on it.
Room 12 has a second door that opens onto the courtyard. That door was found unlocked. Muddy sneaker prints lead from the courtyard door to the display case and back. It rained during lunch, and the courtyard is still muddy. The display case latch is not broken.
Three students were in Room 12 earlier that afternoon: Rosa, Theo, and Wren.
Rosa says she went to robotics club in the library at 3:00. The club sign-in sheet shows “Rosa M. — 2:58.”
Theo says he practiced soccer in the courtyard until 3:45. He is wearing soccer cleats, which are muddy.
Wren says she left at 3:00 and rode the 3:05 bus home. The bus driver remembers Wren getting on.
Part 2: Analyze the case.
1. Which suspect's alibi is weakest? Explain what the evidence shows and what it does not show. Cite at least two details from the case file.
2. Many readers blame Theo first. What evidence makes him seem guilty? What evidence points away from him? Cite the text.
3. Write one inference about how the trophy was taken. List every detail from the case file that supports it.
4. Name one piece of new evidence a detective should look for next, and explain which assumption it would test.
Part 3: Statement sort cards. Cut apart and sort into Evidence, Inference, and Assumption.
Try it on your smartboard
The same statement sort, on screen. Drag each statement to where it belongs — works with touch, a stylus, or a mouse. Ask students to cite the case-file line for every inference.
Evidence
Inference
Assumption
Background for the teacher
The line between inference and assumption is the heart of this lesson, and it's not about whether a conclusion is true. An inference is a conclusion the text supports with specific details you can point to; an assumption is a conclusion that goes beyond what the details show or ignores details that cut against it. “The thief came in through the courtyard door” is an inference because several details converge on it: the unlocked courtyard door, prints leading from it, and a wet hallway with no prints. “Rosa stayed in the library all afternoon” is an assumption, because a 2:58 sign-in shows where she was at one moment, not for the next half hour.
The case file deliberately sets a trap. Theo is the obvious suspect — muddy, in the courtyard — but the prints are sneaker prints and he's wearing cleats. Students who blame Theo are usually reasoning from a feeling of fit rather than from the specific details. The case is intentionally left unsolved: the point is to judge how well each conclusion is supported, and to notice that “the thief must be one of the three students” is itself an assumption the case file never establishes.
Differentiation
Support: Give students a sentence frame for each category: “The text says ___” (evidence); “Because the text says ___ and ___, I can conclude ___” (inference); “Nothing in the text shows ___” (assumption). Reduce the sort to six cards.
Extension: Ask students to write one new fact for the case file that would turn an assumption card into an inference, and one that would turn an inference card into a mistake.
ELL support: Pre-teach alibi, custodian, courtyard, cleats, and latch with images, and read the case file aloud before independent work.
IEP/504 support: Provide the case file with key details pre-highlighted, allow Part 2 responses to be dictated or given orally, and require two cited details instead of three.
Answer key (for teachers)
Part 3 — Sort. Evidence: courtyard door found unlocked; Rosa signed in at 2:58; prints are sneaker prints; bus driver remembers Wren. Inference: taken between 3:00 and 3:30 (in the case at 3:00, missing at 3:30); came in through the courtyard door (prints from that door, no prints in the wet hallway, hallway door locked); opened without force (latch not broken). Assumption: Theo took it; Rosa stayed in the library all afternoon; the thief must be one of the three students.
Part 2 — Analysis (open-ended). Accept reasoned answers with accurate citations. Strong responses typically note: (1) Rosa's alibi is weakest — the sign-in shows she arrived at 2:58 but not that she stayed, and the library is in the building; Wren's bus-driver witness is stronger. (2) Theo seems guilty because he was in the muddy courtyard, but the prints are sneaker prints and he's wearing cleats. (3) e.g., the thief entered and left through the courtyard door, supported by the unlocked door, prints leading to the case and back, and the print-free wet hallway. (4) e.g., matching the sneaker prints to someone's shoes, or asking the robotics advisor whether Rosa left early.
Digital extension (optional)
For a lighter warm-up on the same habit of mind — only trust what the clues actually say — try a case in Sleuth Scouts. It's built for younger players, so it also works well as a peer-tutoring activity with a younger buddy class.