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| Our system’s deep dependence on the human witness shapes a number of fundamental
theories of trial persuasion. To take advantage of the key features of the human witness, we must
first identify and understand them. In this article we analyze those basic features. |
PART I:
THE HUMAN
WITNESS.
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THE HUMAN INTERMEDIARY.
Immersed in our system of dispute resolution, we often fail to recognize (and take
advantage of) its key features.
 Consider the dispute resolution system developed by another rational culture, ancient Greece. Greek
persuasion “handbooks concentrated on what was called ‘argument from probability’ to the neglect of
using direct evidence. Greek juries distrusted direct evidence such as witnesses or documents because
they thought these might be bribed or faked. They put more confidence in what those involved would have
been likely to do in terms of the circumstances or their character.”1 Common sense and probabilities trumped the human witness.
By contrast, at center stage in our dispute resolution system is the live witness.
We consider the best form of proof to be an eyewitness to the key event. We
revere “direct evidence” and speak disparagingly of proof that is “just circumstantial
evidence.” In our approach, nearly all evidence relies upon a human intermediary —
the evidence passes through (is mediated by) a human mind before it reaches the
trier of fact. Not only are all witnesses human, all documents are created by humans.
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Only a few forms of evidence give rise to direct inferences with no
(or minimal) potential for distortion by a human intermediary. Jurors can
view photographs depicting relevant facts (e.g. the extent of injuries on
the face of a victim of spousal abuse) and draw conclusions that are unaffected by a human intermediary.
Sometimes the jury can draw conclusions directly from a piece of real evidence (e.g. the rock that was
used to strike the blow), or from physical attributes of a witness (e.g., the size and strength of a body-builder
who claims to be the victim of an assault by a much smaller person), or from a direct view of the scene of a
crime or accident. But such examples comprise a small fraction of the proof in most cases.
As a result, nearly all evidence is subject to attack or support based on the
presence or absence of factors that create errors in human evidence.
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How do we make any practical use of this insight? The presence of a human
intermediary for evidence means that the evidence is subject to human error. And
the potential for such error provides a basis for diminishing or magnifying the
probative value of almost all evidence. Some spheres of trial practice are very
familiar with a few of these tactics. For example, criminal lawyers frequently examine
witnesses on the accuracy of their identification of the accused. But many potential
arguments (and, therefore, lines of cross or direct) are overlooked. |
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INPUT, STORAGE, AND OUTPUT.
To begin to identify these overlooked arguments we can contrast proof
through a live eye-witness with proof through photograph, which is the archetype of proof without an intermediary.
 When a human intermediary is the witness for a certain piece of information, that information
must be (i) detected out-of-court by the witness’s five senses, (ii) stored in human memory,
and then (iii) transmitted out (usually in words) through testimony or demonstration on paper (or other media).
When a jury is asked to draw inferences directly from a photograph, there is no human intermediary and none of those steps occur.
From this we glean that errors arise in three different settings: during input, storage, and output.
Furthermore, errors in each of these three settings fall into two different types: physical limitations or mental distortion.
In the following Part, we identify the sources of errors in perception, memory, and communication. By explicitly recognizing and
cataloguing these sources of error, we have both a useful tool and a starting point for deeper analysis. We
can use it as a checklist of potential lines of cross and direct examination to undermine or support testimony. And we can take individual items on this list
and delve deeper to understand patterns of examination that make the best use of each potential error. |
PART II.
SOURCES OF
HUMAN WITNESS
ERROR. |
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A. PERCEPTION: INPUT ERROR.
One type of input error occurs because of physical impediments to perception that prevent the witness from accurately or
completely perceiving the event. For example: a witness did not see the incident well because the parking lot was too dark.
A second (and more subtle and more important) type of input error is caused by misinterpretation.
Humans do not simply record the light and sound images directly to memory. Instead, we
(a) interpret the sensory images, and then
(b) remember the interpretations.
It is true that we remember a passing blue car because we perceive a passing blue car. But we
perceive a passing blue car only because we interpret the movement of the blue light and the accompanying
sounds as a passing car. We edit, filter, group, and interpret our sensory input from the moment of initial
perception. As a result, the perceptions themselves are “distorted” interpretations before they ever reach memory.
In the following two sections, we separately analyze the sources of interpretation
errors during input and then physical perceptual errors. |
PART II.
CATALOGUE OF
PERCEPTUAL ERRORS CAUSED
BY INTERPRETATION |
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The following is a catalogue of factors that diminish or magnify interpretation errors during perceptual input.
a. WELL-DEVELOPED PERCEPTUAL JUDGMENT,THROUGH EXPERIENCE OR TRAINING
 People can develop an enhanced ability to perceive subtleties. For example, a professional line judge
in tennis may not have better physical vision than the average tennis fan but, because of experience
and training, can actually “see” more acutely whether the pale green tennis ball traveling at
120 m.p.h. hits the three-inch wide chalk line.
b. COMPETING PERCEPTIONS
Competing perceptions can impede our efforts to perceive the relevant event. This competition can
take the form of a large number of competing inputs or by inputs with greater stimulus (brighter, louder,
bigger) than the relevant event. This is the “Where’s Waldo?” effect. |
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c. BIAS OR INTEREST
Our desire for a certain outcome colors our immediate interpretation of what we
see. Did the football receiver place a foot out of bounds before catching the ball?
A die-hard fan is more likely to get that call wrong than a neutral referee.
d. LENGTH OF TIME EXPOSURE TO EVENT
If someone perceives an event longer, there is greater
likelihood that the person will accurately observe the event. This limitation on input is also related to
sources of memory error (discussed below), including the ability and motivation to immediately replay the
event in the mind or to double-check the perception.
e. INTENTIONAL MENTAL FOCUS
An observer can choose to place mental focus principally on interpreting visual or aural cues, or
instead on some other phenomenon (such as recalling last weekend’s trip to the lake or thinking about a problem to be solved at
work). A mind focused at the moment of perception on interpreting the perception will perceive more and perceive it more accurately.
f. MOTIVATION TO PAY ATTENTION
A witness may have a particular motive to pay attention to or avoid perceptions.
For example, the bank patron may pay particular attention to physical features of
the bank robber during the robbery. By contrast, the squeamish person may avoid
looking at the gory accident scene.
g. ALTERNATIVE OR MULTIPLE ANGLES OR SOURCES
The sports world shows us the importance of the right camera angle. If we perceive
an event or phenomenon from one angle, we are more likely to misinterpret
it than if we view if from more than one. For example, if we see a body at a crime
scene from a single angle we cannot interpret it as well as we can were we to
walk all around the scene.
h. DRUGS, ALCOHOL, OR OTHER RELATED IMPEDIMENTS TO INTERPRETATION
Drugs and alcohol can, obviously, distort the interpretation of perceptions. |
2.
CATALOGUE OF
PERCEPTUAL ERRORS CAUSED
BY PHYSICAL EFFECTS. |
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The following is a catalogue of factors that diminish or magnify physical
errors during visual input. We follow this with a similar identification of aural perception errors.
a. Lighting — Too little or too much.
b. Distance — Too far away or too near.
c. Vision — Near-sighted or far-sighted
d. Color-blindness.
e. External obstructions.
Any object placed in the
visual field between the eye and the event can partially
obstruct visual input. Glasses, sun-glasses, or goggles
can block, distort, or diminish visual perception.
Clothing, such as a hat, helmet, or high collar can block
or limit views. Vision can be blocked or limited by other
people who are with or near the witness or by other
obstacles such as buildings or trees. Vision can also be
impeded by “other-sidedness.” By that we mean that
the relevant fact was primarily visible from the other
side of the object or person that is the subject of the observation (e.g., a gun in the
right hand of a person whose left side was exposed).
The following is a similar catalogue of sources of error for aural perceptions
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a. Loudness.
b. Frequency – higher pitched
sounds do not travel as well
as lower pitched sounds.
c. Distance from the sound.
d. Obstructions. |
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e. Echoes.
f. Wind. Because sound is
ordinarily transmitted through
air, the movement of the transmitting
medium (i.e. wind) can
distort (muffle or amplify) sound.
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