Introduction

Personal Knowledge Requirement

Introduction

Imagine a witness who takes the stand in a car-crash case and announces that the defendant ran the red light. The jury would naturally want to know how the witness knows that. If the witness stood at the corner and watched, the statement is valuable evidence. If the witness only heard it from a neighbor the next morning, the statement is a rumor delivered under oath. The law of evidence has to separate those two witnesses before the jury hears either one, and the first question of this chapter is how it does so.

The tool is Federal Rule of Evidence 602, which sets a threshold for every lay witness. Under the rule, a witness may testify to a matter only if evidence is introduced sufficient to support a finding that the witness has personal knowledge of the matter.¹ Personal knowledge means knowledge the witness gained firsthand, through the witness's own senses, as opposed to a belief assembled from what other people have said. The same rule adds that the witness's own testimony may supply the proof of personal knowledge, and that the requirement does not apply to expert testimony under Rule 703.² The reason for the requirement follows from its structure: a jury can weigh only what a witness actually perceived, and a witness who relays a secondhand impression gives the jury nothing it can test through cross-examination of that witness.

The first analytical step is to ask what the witness is being called to describe, and whether the evidence shows that the witness was positioned to perceive it. Notice that the rule demands only enough proof to support a finding, which is a lower bar than proof that the witness definitely perceived the matter. The chapter proceeds in order: what personal knowledge means, how the foundation is laid and who decides whether it is adequate, how the requirement differs from the hearsay objection, how it interacts with competency, lay opinion, and expert testimony, and how it plays out in ordinary trial rulings. It begins with the meaning of personal knowledge itself.