Thursday, September 29, 2016

10 Dubious Sources of Criminal Evidence

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)





















No comments:

Post a Comment