Fact, assumption or question: how to think like a detective

On the desk, every mark you make is one of these:

• Fact. What the page shows. It is on the page, in black and white.
• Assumption. What you are treating as true for now, without proof.
• Question. What you still need answered.

The desk draws them differently on the page: a solid box for a fact, a dashed one for an assumption, a red one for a question. Your notebook sorts them into three lists.

Here is one way to sort it.

• Fact: the neighbour says the van passed at about quarter past eight. The neighbour says the gate was open, and that the dog was loose.
• Assumption: the gate was left open on purpose. Nothing on the page says so.
• Question: who last used the gate? Where was the dog shut in at night?

Look closely at that first fact. It is a fact that the neighbour says it, which is not the same as the van really passing at 8:15. A camera log later might make it a fact of the stronger kind. Until then, mark exactly what the page says.

An assumption does not stay small. “The gate was open on purpose” becomes “somebody wanted the dog out”, which becomes a motive, and three steps later you have a theory built on one sentence that nobody checked.

Questions are the opposite: they are cheap and they point somewhere. Writing one down tells you what to look for in the next exhibit. Keep facts and assumptions apart, because a case punishes people who treat one as the other.

Sort these three invented lines, then check your answers.

1. “The shop receipt is stamped 08:31.”
2. “The driver must have been in a hurry.”
3. “Why does the receipt show two coffees?”

1. Start by quoting the page. Say what it says before you say what it means.
2. For an assumption, say why you are making it, and what would prove it wrong.
3. Revisit your assumptions. Promote one to a fact only when an exhibit supports it, and drop it when one does not.