What Personal Knowledge Means

What Personal Knowledge Means

Rule 602 is three sentences long, and each sentence does separate work. The first sets the threshold: 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 The second adds that the witness's own testimony may supply that evidence, and the third carves out expert testimony under Rule 703.² This section concerns the first sentence, and in particular the phrase on which everything else depends, "personal knowledge." The second and third sentences each receive their own treatment later in the chapter.

Personal knowledge means knowledge gained through firsthand observation or experience, as distinguished from a belief based on what someone else has said.³ The rule's reach follows from that definition. Admissible lay testimony is limited to matters the witness acquired through any of the witness's own senses, which means sight, hearing, touch, smell, or taste.⁴ Because the requirement attaches to the witness's source rather than to the subject matter, it applies to testimony about any fact that a person could perceive: the color of a traffic signal, the speed of a car, the smell of gas in a hallway, the words someone spoke. Whatever the fact, the question put to the witness is the same: how do you know?

The reason for asking lies in what cross-examination can reach. A witness who perceived an event can be questioned about where she stood, how well she could see, whether she was paying attention, and how clearly she remembers. Each answer gives the jury something to weigh. A witness repeating a rumor offers nothing comparable, because the person who actually perceived the event is absent from the courtroom and cannot be tested. The rule therefore screens out testimony whose real author never appears, and it also keeps the jury from mistaking a confident repetition of someone else's belief for an observation.

Two contrasting pairs show the line. A witness has personal knowledge that a street was slippery on a given day if she walked on it, slipped, or otherwise saw or felt its condition.⁵ A different witness may believe the street was slippery only because a friend said so. That witness has personal knowledge of one thing, namely that the friend thought the street was slippery, and has none of the street's actual condition.⁶ The same split appears in a car-crash trial. A passenger who watched the signal change can say it was red. Imagine instead a passenger who admits he never looked at the signal and learned its color only from the driver's remarks afterward. His statement that the light was red rests on someone else's report, so the testimony cannot stand and should be stricken.

The second pair also shows how the objection works in practice. When a witness concedes being in a distant place at the moment of the event, the proper objection is lack of personal knowledge. When the witness says another person told her about the event, the proper objection is hearsay, a distinction developed in a later section.⁷ Both objections respond to the same weakness, a missing firsthand source, but they are triggered by different testimony. For now the practical consequence is the one the rule's first sentence announces: the party offering the witness must put in enough evidence to show the witness was positioned to perceive what she describes. How much evidence is enough, and who decides, comes next.

Firsthand Perception Through the Senses

The definition of personal knowledge turns on how the witness came to know a fact, and Rule 602 allows that source to be any of the witness's own senses.⁹ Sight is the usual channel, but a witness who heard a crash from inside a house, felt a floor go slick underfoot, or smelled smoke in a stairwell has perceived the fact just as directly. The rule attaches to the channel of acquisition, so each witness is limited to what that channel actually delivered. The listener inside the house can describe the sound of the collision, yet cannot say what color the signal was.

A second question follows: how sure must the witness be about what she perceived? Most courts hold that uncertainty does not require exclusion for lack of personal knowledge. A witness who testifies from her own observation but is unsure of some detail may qualify her answer with phrases such as "I believe," "I think," or "it is my impression" without losing admissibility.¹⁰ The reason comes from what the rule measures. Rule 602 asks whether the witness actually experienced the event, not whether she is confident about it. If certainty were the price of admission, the foundation requirement would turn into a credibility test, and credibility is for the jury to decide after hearing the answer and watching the cross-examination. The hedge is itself information, because it tells the jury how much weight the observation can bear.

Consider an invented neighbor who was watering her lawn when a truck passed and who testifies, "I think it was doing about thirty-five." She saw the truck, so her estimate rests on perception, and the qualifier goes to weight. Courts accept this kind of answer readily, since a lay witness can hardly describe a vehicle's speed except in miles per hour, and speed of a vehicle is treated as a standard example of acceptable lay testimony.¹¹ The same logic covers the everyday inferences people draw from what they have seen. We often "know" a fact because of many small observations we could not list on demand, and a court will not object to such testimony unless it touches an important issue. If it does, and the true basis for the conclusion turns out to be a conversation, an objection for hearsay or lack of personal knowledge will be sustained.¹²

Change one fact and the answer reverses. In Gorby v. Schneider Tank Lines, a driver in the opposite lane testified that the tanker's driver "did everything he could" to avoid a collision, and the trial court excluded the testimony. The court of appeals affirmed, because the witness was not in the tanker's cab and so could not know what measures its driver took or when he first noticed the other truck. Even a witness in the cab would not have qualified without evidence that he knew the truck's brakes, steering, load, and stopping distances.¹³ The neighbor's hedge concerned how well she perceived something she saw, while the opposite-lane driver had not perceived the matter he described at all. A hedge can cure the first situation. Nothing in the testimony can cure the second, since confidence cannot supply a perception the witness never had.

Background Facts and Practical Tolerance

The rule that a witness must have perceived what she describes meets its first practical limit in the opening minutes of almost every direct examination. Lawyers begin by asking a witness for her name, where she was born, who her parents were, and when she was born. Imagine a witness named Emma Harris who answers each of these questions in turn: she was born in Bangor, Maine, to Algernon and Anne Harris, her mother's maiden name was Davies, her parents emigrated from Yorkshire in 1984, and her birthday is November 14, 1991. Ms. Harris cannot have perceived any of this herself. She was an infant at her own birth, and everything she knows about her parents' origins and her own birth date she learned from what her family told her.¹⁵

Taken literally, then, every answer lacks personal knowledge. The more familiar label for the problem is hearsay, since the information is in substance a repetition of what other people said. Technically, though, hearsay is not quite the right objection, because Ms. Harris never refers to anyone's statement. The objection that fits her answers is the one Rule 602 supplies, which asks whether the witness has knowledge gleaned directly from her own senses, and she plainly does not.¹⁶ Yet courts do not sustain that objection. Such answers are routinely accepted without a second thought, even though lawyers and judges recognize the problem.¹⁷

The reason is that the rule exists to keep out secondhand testimony whose real source cannot be tested, and that concern has little force here. A system that refused to take a witness's word on her own name, parentage, and birthplace would produce delay and nothing else. No one doubts the facts, no one disputes them, and the witness's report is as good a source as any available. The foundation requirement guards the jury against relying on a rumor that matters to the outcome. A background fact that nobody contests presents no such danger, so a judge who overrules the objection loses nothing the rule was written to protect. The jury also gains something from these opening questions, because it learns who is speaking before turning to the issues.¹⁸

This tolerance is a matter of trial practice. Rule 602 contains no exception for family history or background information, so the flexibility rests on the judge's judgment about when an objection would obstruct the trial rather than improve it.¹⁹ The practice also has a boundary, and the boundary is contestedness. Suppose that in a dispute over citizenship or entitlement to benefits, the place of a litigant's birth is the central contested fact. The same secondhand testimony then carries a real risk of error on a point that decides the case, and an objection stands on much firmer footing. The source materials suggest that judges would still likely admit the answer, but it might carry little weight if the other side has official records or other strong proof pointing the other way.²⁰ Where the secondhand matter is substantial and disputed, indirect proof does not get the leniency given to harmless background.

The contrast with the earlier examples in this chapter is therefore a contrast in what is at stake. The passenger who learned the signal color only from the driver's later remarks was describing the very fact the trial would decide, and his testimony could not stand. Ms. Harris describes facts that serve to identify her and that nobody has any reason to dispute. The lack of firsthand perception is identical in both, and the difference in treatment comes from how much the fact matters and how seriously it is contested.