Copyright 2018 by Gary \L. Pullman
Lie-detector
results aren't admissible in U. S. courts of law. Such devices can't
determine whether an individual is lying. They simply measure blood
pressure, heart rate (pulse), and other physiological indicators of
emotion. Some people can use various tricks to “fool” a
lie-detector, too. In many cases, examiners persuade a person the lie
detector shows he or she is being dishonest, causing the individual
to make false confessions. (LINK 1)
Many
of us are aware of the limitations of lie-detector tests, but we may
not realize that other sources of criminal evidence thought to be
reliable are also often undependable. The relative unreliability of
tests which, in the eyes of the general public, are often considered
dependable, or even certain, indicators of criminal guilt has had
serious consequences, as defendants have been incarcerated, denied
parole, or even executed on the basis of such evidence.
This
list of 10 dubious sources of criminal evidence focuses on evidence
used in U. S. criminal trials, although it may also apply to such
litigation in other countries.
10
Eyewitness Testimony
Eyewitness
testimony is notoriously unreliable. Experiments have shown that, due
to lying, faulty or incomplete memories, false memories, mistaken
perceptions, and bias, eyewitness, or anecdotal, evidence can sound
convincing but be partially, largely, or even completely mistaken.
(LINK 2)
Eyewitness
testimony can also be “contaminated by beliefs, later experiences,
feedback, selective attention to details.” Likewise,
“exaggeration,” confusion concerning the chronology of events,
misinterpretation, delusions, and other factors often make eyewitness
testimony unreliable. (LINK 3)
9
Fingerprints
Fingerprints
are often regarded as infallible proof of innocence or guilt, but, as
evidence of a crime, they, too, can be more problematic than many
people may realize. No standard exists by which to determine when one
fingerprint matches another. Experts sometimes require a number of
fingerprint features, or “points,” to match, but no set number
must do so. Some say matching 6 points is sufficient. Others require
9 points to match. Still others insist 12 is the minimum number of
matching points. Some fingerprint experts reject the point system
altogether. What are the odds two fingerprints will “share certain
ridge characteristics”? No one knows. There's no standard. There's
also no way to know how often an examiner may erroneously “match”
two prints or mistakenly conclude fingerprints from different sources
are those of the same person. It's been shown, however, that in a
“1995 test, 34 percent of test-takers made an erroneous
identification,” and “latent prints” may be even more often
misidentified or “matched.” Although fingerprints are admissible
in court as nearly certain indicators of guilt or evidence, their use
has never been subjected to rigorous courtroom challenges, or
“adversarial testing,” or to “empirical study.” (LINK 4)
8
Confessions
Twenty-five
percent of the people who confess to crimes are later exonerated by
DNA. People make false confessions under duress, but also because of
“coercion, intoxication, diminished capacity, mental impairment,
ignorance of the law, fear of violence, the actual infliction of
harm, the threat of a harsh sentence,” and “misunderstanding the
situation.” Confessions by “juveniles” are the most often
“unreliable” admissions of guilt. Police interrogators often lie
to suspects about the actions of district attorneys or judges and
often invent or exaggerate evidence or lie about the suspect's legal
situation to pressure suspects to confess. (LINK 5)
7
Criminal Profiling
Criminal
profilers may assume criminal behavior always has the same motive or
purpose, whereas, in fact, the motive may differ from one person to
another. Research shows investigators tend to “validate” a
profiler's “claims” if they wish him or her to be “right,”
even suppressing information that doesn't fit the profile. LINK 6)
A
detective may purposely interpret a situation in several ways, making
“vague or ambiguous statements” to which nearly anyone is likely
to agree. When the suspect concurs with one of these statements, the
detective, using “observation” and other cues, “reads” the
suspect, providing more statements and claims with which he or she is
likely to assent. While the process may be effective, it has little,
if any, evidentiary value. (LINK 7)
6
Handwriting Analysis
Handwriting
analysis is often used to assess the authenticity of document
signatures and writings, as it was to validate the signature of Adolf
Hitler so his documents could be entered as evidence in war crimes
trials. (LINK 8)
According
to a 2009 report by the National Academy of Sciences, little
“research” supports the “reliability and replicability of the
practices used by trained document examiners.” Furthermore, the
Journal
of Forensic Sciences
found “document examiners were almost twice as likely to make
errors when viewing hand-printed writing as they were when viewing
other types of documents, such as those written in cursive.” Some
judges, law professors, lawyers, and handwriting analysts challenge
not only the accuracy, but also the very possibility, of obtaining
scientifically valid conclusions based on the way a person shapes,
spaces, and executes his or her letters. Interpretation is often
arbitrary. In a word, Mark Denbeaux, a Seton Hall University law
professor, regards the whole practice as “bogus.” (LINK 9)
5
Penile Plethysmograph
The
penis plethysmograph measures the flow of blood through the penis,
“by measuring minute changes in . . . erectile responses,” which
supposedly indicates the level of sexual arousal a man experiences,
often while he is exposed to pornography or other titillating
materials. The device, employed in many “sex offender treatment
programs,” is sometimes required “as a term of supervised
release” to determine whether a parolee is “at increased risk of
reoffending.” The device's efficacy has been challenged on numerous
occasions, and courts have not always ruled it an effective indicator
of male sexual arousal. (LINK 10)
Critics
of the penile plethysmograph contend the use of the device produces
conflicting results. Both sex offenders and men who have not
committed sexual offenses have been sexually aroused by the same
“stimuli.” Paradoxically, many sex offenders are not aroused by
materials that suggest acts similar to those which they've committed.
Some courts refuse to admit evidence obtained through the use of the
device, because of its “questionable reliability,” and because
there's no verified correlation between its findings and the actual
behavior of either criminal suspects or convicted sex offenders.
There's also the problem of the “lack of standardized materials to
use as stimuli for subjects.” Constitutional issues are also
involved in the use of the device. For these reasons and others, it's
not universally considered a reliable source of criminal evidence.
(LINK 11)
4
Vaginal Plethysmograph
The
vaginal plethysmograph is used for many of the same purposes as the
penile version, but its “probing for signs of arousal is considered
“no more reliable than penile measurements” because no “sound
theoretical basis” exists “for interpreting what the measurements
mean.” If anything, the vaginal version is even more dubious as a
source of criminal evidence than its penile counterpart, “because
it measures the amount of blood in the genitalia by monitoring minor
changes in skin color inside the vagina, and it's difficult, if not
impossible, to determine what changes in skin color actually
represent. (LINK 12)
The
accuracy of the vaginal plethysmograph is also undermined by its
“inability to measure sexual responses during orgasm due to the
sensitivity of the probe to movement artifact.” Even when orgasm
isn't an issue, the possibility of interpreting the device's readings
with any precision is highly questionable, since increased vaginal
pulse amplitude (VPA) may result from “a restriction” in
“drainage” from veins instead of “vasodilation per
se.”
In addition, vaginal blood volume and VPA “signals” don't
indicate which blood vessels “the vasodilation” occurs in. (LINK
13)
3
Repressed Memories
Research
shows jurors in mock trials are apt to accept the authenticity of
repressed memories if they also believe the defendant's claims. When
jurors don't believe the defendant's claims, they often think the
“false claims” result from “an
honest mistake” rather “than a deliberate lie.” If
two witnesses testify, one of whose memories are not repressed and
the other of whose memories are repressed, both male and female
jurors are “more skeptical” of the latter witnesses' testimony.
(LINK 14)
Although, in general,
psychologists tend to believe people sometimes repress memories of
traumatic events, there's “no controlled laboratory support for the
concept of repression,” and, based on other factors in the case,
jurors may not accept the validity of such phenomena, making
repressed memories a dicey defensive strategy. (LINK 15)
2
Jail House “Snitch” Testimony
Prosecutors
sometimes offer a “favorable plea to a lesser charge or a reduction
in sentence” to prisoners who testify concerning information they
hear from cellmates, despite the fact that a
recent report “found that prosecutions based on the testimony of a
'snitch' are the leading cause of wrongful convictions in capital
cases.” Paul Butler, a professor at George Washington University
Law School and a former Assistant United States Attorney, identifies
other problems with using such testimony, contending, for one thing,
“the widespread and unregulated use of snitches impedes community
safety” and “makes the evidence in criminal cases unreliable.”
(LINK 16)
1
Roadside Drug-testing Kits
Two-dollar
roadside drug-testing kits have come under fire in several U. S.
states because their use has resulted in false positives and have
led, in some cases, to false confessions. False positives have
resulted from “80 compounds, including
common home cleaning products.” (LINK 17)
Color changes supposedly
indicated the presence of cocaine, but scientists have determined
color changes can suggest only the “possible presence or absence of
a particular molecule grouping.” In addition, the integrity of
these tests is compromised by the fact that color identification is a
subjective process, and “it is not uncommon for two analysts to
describe the same color differently.” (LINK 18)
LINK
4: http://issues.org/20-1/mnookin/
LINK
11: http://skepdic.com/penilep.html
LINK
12: http://skepdic.com/penilep.html
LINK
16:
http://www.rhuntlaw.com/blog/2015/03/jailhouse-snitches-dont-go-to-the-pen-send-a-friend.shtml
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