Excerpt
from Scientific Evidence in Civil and Criminal Cases, 4th ed. (1995) by
Moenssens, Starrs, Henderson & Inbau, Chapter 19, at pp. 1171-1180.
. . .
§ 19.15
The Inherent Unreliability of Eyewitnesses—True or False?
The chronicles of legal history are filled with tragic cases
of mistaken identity. The tale of Berson and Morales echoes that of hundreds of
thousands of others. In the 1970s, Lawrence Berson was accused of several rapes
and George Morales was accused of robbery. Both men were picked out of police
lineups by victims of the respective crimes and both men were innocent. Berson was
cleared when another man, Richard Carbone, was arrested and implicated in the
rapes. Carbone was convicted on the rape charges and later confessed to the
robbery, clearing Morales.
Regrettably, it is impossible to know how many innocent men
and women have been sentenced to prison or death on the basis of faulty
eyewitness testimony. However, it has been estimated that more than 4,250
Americans per year are wrongfully convicted due to sincere, yet woefully
inaccurate eyewitness identifications. Over the past fifty years, scientific
research has revealed that eyewitness testimony is often an incorrect account
of what actually took place. Scientists now know that the human mind does not act
as a video camera meticulously recording and replaying everything within its
viewfinder. Rather, human memory is a complex process which is vulnerable at
every stage. This knowledge, in turn, has led attorneys to invite psychologists
who have done studies on these issues to testify to their conclusions when the
critical evidence was that of occurrence witnesses. Most of the cases wherein
this testimony has been offered have been criminal prosecutions involving
eyewitness identifications of a defendant, though the principles of perception,
memory, and recollection are applicable equally to event witnesses in civil
litigation.
§ 19.16
Perception, Memory, and Recollection
The acquisition of information into memory involves a three-step process. At each stage of the process, errors are possible. During acquisition, the first step in the memory process, an event is perceived and information "bits" are initially stored in memory.
In the second stage, information is held or retained in
memory. In the final stage, memory is searched and pertinent information is retrieved
and communicated. In the acquisition stage, information is "encoded"
into a person's memory system. However, every detail of an experience is not
encoded; the human mind can only process a fraction of the rapidly incoming
physical stimuli. Both consciously and unconsciously, the observer determines
which details are actually encoded according to where his or her attention is
focused.
The physical aspects of an event are obviously compromised
by the selective nature of the acquisition stage of memory. However, matters
are further complicated by the fact that acquisition also involves a social
component. Thus, a witness' ability to perceive accurately is affected by both
event factors—those inherent to the event itself—and witness factors—those
inherent to the witness.
1. INFLUENCE OF THE EVENT FACTORS
Event factors include duration of the event, complexity of
the event and violence of the event witnessed. Common sense and science show
that increased exposure time improves the accuracy of witness perception.
However, witnesses generally overestimate time and have great difficulty gauging
the duration of an event. For example, Professor Buckhout, a cognitive psychologist,
staged an assault during one of his classes. The assault actually lasted 34
seconds, but the average estimate of time by 141 witnesses to the event was
overestimated by a factor of almost two and one half to one (2.5:1).
Complexity of the event witnessed has a direct effect on the
encoding of information. Psychological research has shown that complex events
are more difficult to recognize and encode into memory than more basic events.
For example, a street fight among multiple parties is less likely to be
recollected with accuracy than a fight between two parties.
Violence also affects a witness' acquisition of information.
In 1978, an experiment was conducted in which subjects viewed violent and
non-violent tapes of an event. The subjects who viewed the violent version of
the event had more difficulty perceiving and recalling the event than those
subjects who had seen the non-violent version.
2. INFLUENCE OF PERSONAL FACTORS
In addition to event factors, perception is also affected by
witness factors. Witness factors include stress, weapon focus, and expectation.
Lay persons believe that stressful events accentuate memory, that what is seen
or heard during periods of high stress is more accurately recorded and
recalled. However, empirical data indicates that stress, anxiety and fear
disrupt the normal perception process and distort subsequent memory. Thus, a
witness' statement that he was "so frightened that his (the criminal's) face
is etched in my memory forever" is a psychological oxymoron.
Psychologists term the relationship between stress and
memory as the Yerkes–Dodson Law. The Yerkes–Dodson Law depicts the relationship
between stress and memory as an inverted "U" curve. At low arousal,
memory is low. Memory improves with increased stress levels to a point (optimal
performance). After the point of optimal performance, memory decreases with increased
stress levels. Thus, it is not uncommon for a witness to recall the details of
crime less accurately than they recall routine events.
Psychological research has also shown that people under
stress tend to concentrate on those aspects of an event or experience which
they feel are most important. Weapon-focus is an example of this psychological
phenomenon. An individual faced with a gun held to their head is likely to
concentrate on the gun to the complete exclusion of the attacker's face or
physical characteristics.
As early as 1909, it was noted that expectation has a
profound effect upon perception: "observation is peculiarly influenced by expectation,
... we tend to see and hear what we expect to see and hear." Modern
science can now account for the relationship between expectation and
perception. As noted earlier, the human mind can only process a fragment of the
physical stimuli digested by the senses. The mind compensates by integrating
the stimuli with concepts based upon a fund of general knowledge acquired over
time or, put more simply, with expectation. In this manner, individuals
subconsciously reconstruct events from what they assume must have occurred.
Expectation includes personal biases, cultural biases,
temporary biases, latent prejudices, and stereotypes each of which have the ability
to influence acquisition. For example, a group of subjects were shown a
photograph of several people standing in a subway train, including a white man
holding a razor and apparently arguing with a black man. When asked to describe
what they had seen, over half of the participants reported that the black man
had been wielding the razor.
3. INFLUENCE OF STORAGE FACTORS
Memory is also susceptible to extraneous influences during
storage, the second stage of the memory process. Memory of events decays over
time. Although an individual may accurately perceive an event, its
representation in the observer's memory system will not remain intact for very
long. Considerable memory loss is likely to occur between an event and an
eyewitness' actual identification of a suspect in a criminal case. The human
mind actively fills the gaps created by long-term memory loss; this gap-filling
process introduces inaccuracies into memory for the sake of a
"complete" picture. Obviously, this process has great implications
for the criminal defendant.
Lay persons tend to believe that there is a positive
correlation between witness confidence and memory accuracy—that the more conviction
a witness has the more likely his or her testimony is to be an accurate
depiction of the event. However, psychological research indicates that there is
in fact a negative correlation between a witness' confidence in his or her
memory and the accuracy of that memory. Thus, the more confidence a witness has
in his or her memory, the more likely the witness' memory of the event is
inaccurate. Again, this counter-intuitive psychological principle has far
reaching ramifications for litigants.
An individual's memory system may also be augmented or
altered during the storage stage by intervening occurrences. For example, a
witness may read or hear about an incident he or she observed. The mind tends
to incorporate post-event information such as that conveyed by the article or
discussion with that previously encoded from the incident itself.
In 1976, Dr. Elizabeth Loftus conducted an experiment to
demonstrate how post-event information in the form of questioning can affect
memory. In this experiment, subjects viewed a videotaped auto accident and were
questioned about what they observed.
A week later the subjects were again questioned. They were
asked "did you see any broken glass?" The videotaped accident in fact
did not involve broken glass, but those subjects who had been questioned
earlier with the verb "smashed" were more likely to assert that they
had seen broken glass in the video tape. A memory was formed when the subjects
viewed the tape, but it was later augmented and altered by the suggestive
questions of the interviewers. The implications of this study on police
questioning techniques and general investigative procedures is obvious.
4. INFLUENCE OF RECALL FACTORS
The final stage of memory, retrieval, is also vulnerable to
outside influences. For example, social factors may influence the witness'
recollection of events, especially in the criminal identification setting.
Eyewitnesses, like other people, do not want to appear foolish. By arranging a
line-up, police officials suggest to an eyewitness that they have apprehended
the culprit. Consequently, the eyewitness may select an individual despite his
or her lingering uncertainty, to avoid "letting the criminal go free"
and to avoid looking foolish.
All of these factors have been stressed by psychologists who
advocate admission of expert testimony on the unreliability of event witnesses
as reasons for their advocacy. However, opponents have been no less vocal, and
thus the legal literature abounds with writings on the issue.
Modern psychological science has revealed much about human
memory and the fallibility of eyewitness testimony in the 200 years since T.
Reid, an influential scholar of his day, wrote:
“... and if a
skeptical counsel should plead against the testimony of the witness, that they
had no other evidence for what they declared than the testimony of their eyes
and ears, and that we ought not to put so much faith in our senses as to
deprive men of life or fortune upon their testimony, surely no upright judge
would admit a plea of this kind. I believe no counsel, however skeptical, ever
dared to offer such an argument; and, if it were offered, it would rejected
with disdain[.]”
Unfortunately,
in this area of endeavor, the American legal system has not embraced the
teachings of modern psychology wholeheartedly.
§ 19.17
What Can Experts Say?
In a jurisdiction where the expert is permitted to testify
on the issue, the witness can explain the mechanism of perception, processing,
memory, and recollection, and describe what empirical research has been conducted
on the subject and what the results are. The expert will ordinarily not be
permitted to testify on the accuracy of a particular witness. In a child sexual
abuse case, in a jurisdiction that accepts opinion evidence in this area of the
law, the expert typically can testify on the problems child victims of abuse
have remembering and describing the incidents of which they complain, but cannot
state whether a particular child was abused on the basis of psychological
evidence, or that the child was truthful when complaining.
§ 19.18
Admissibility of Eyewitness Expert Testimony
Trial courts and appellate courts in America have taken
decidedly different positions on the issue of expert testimony addressing eyewitness
reliability. The majority of jurisdictions continues to exclude eyewitness
expert testimony. However, a growing number of courts have upheld exercise of
the discretionary power of trial judges who exercised discretion in favor of
admitting expert opinion testimony on eyewitness reliability.
* * *
Despite these cases, in the majority of jurisdictions that
have faced the issue, expert opinion evidence on the unreliability of event witnesses
has been excluded. Most of the decisions to prohibit the testimony used as
their rationale that the credibility of any witness is an issue for the jury to
determine, and that to permit such testimony impermissibly invades the province
of the jury. The reasons for exclusion are perhaps best reflected by People
v. Enis, wherein the Illinois Supreme Court said:
"We caution
against the overuse of expert testimony. Such testimony, in this case concerning
the unreliability of eyewitness testimony, could well lead to the use of expert
testimony concerning the reliability of other types of testimony and,
eventually, to the use of experts to testify as to the unreliability of expert
testimony. So-called experts can usually be obtained to support most any
position. The determination of a lawsuit should not depend upon which side can
present the most or the most convincing expert witnesses. We are concerned with
the reliability of eyewitness expert testimony, whether and to what degree it
can aid the jury, and if it is necessary in light of defendant's ability to
cross-examine eyewitnesses. An expert's opinion concerning the unreliability of
eyewitness testimony is based on statistical averages. The eyewitness in a
particular case may well not fit within the spectrum of these averages. It
would be [inappropriate] for a jury to conclude, based on expert testimony,
that all eyewitness testimony is unreliable." [Citations omitted.]
§ 19.19
Path of the Future
Since the advent of the Daubert v. Merrell Dow
Pharmaceuticals, which did away with the "general acceptance"
rule for the admission of novel scientific or expert testimony and replaced it
with a standard of evidentiary reliability, which must be determined by the
trial judge prior to admission, courts, whether they admitted or denied admission
to evidence on the factors affecting the reliability of event witnesses, may
have to revisit the issue and explore whether the "reasoning or
methodology underlying the testimony is scientifically valid and ... whether
the reasoning or methodology properly can be applied to the facts in issue."
That was in fact the reason for remanding the case to the trial court in U.S.
v. Amador–Galvan, and the reason why the Supreme Court remanded U.S. v.
Rincon for further consideration.
Though the American judicial system has been slow to accept the lessons of modern psychology, there does appear to be a growing group of judges willing to accept the logic of the premise of the unreliability of event witnesses and permit expert testimony on that topic. Whether these recent cases signal a trend which will grow, only time will tell. We can only hope that the legal community will, in this case, be as receptive to opinion testimony that has a sound basis in experimental science, as it has been in other novel fields. If so, perhaps one, two, or more innocent people who otherwise would have been convicted of crimes they did not commit will be set free; after all, it is better to acquit 10 guilty persons than to convict one innocent person.