Distinguish knowledge from inference

The idea

A witness’s firsthand observations differ from conclusions drawn from those observations or information received from others. Separating these categories helps an investigator ask precise questions and prevents confidence from being mistaken for direct access to an event.

Worked example

A volunteer says a locked storage room was empty at 9 p.m. Asked how she knows, she explains that she saw the light switched off but never entered. Her observation is that the light was off; her conclusion concerns occupancy. Another volunteer entered at 8:55 and saw no one. Their accounts provide different kinds of evidence. A careful interviewer records each account in its own terms and asks about sightlines, timing, and other possible occupants.

Use it carefully

Federal Rule of Evidence 602 addresses personal knowledge and includes qualifications that this introductory lesson does not exhaust. Expert testimony and other evidence questions require separate rules. In ordinary inquiry, inference is often necessary and useful; it simply should be labeled. The purpose is to reveal the reasoning chain, not to dismiss every account containing interpretation. This is educational discussion, not case-specific evidence advice.

RETRIEVE. REASON. REMEMBER.

Knowledge check.

Choose one answer for each question, then check your reasoning.