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Study: Many courts allow unscientific psychology tests as evidence

On Behalf of | May 11, 2020 | Criminal Defense |

Recently, a report appeared in the journal Psychological Science in the Public Interest that indicated large variability in what psychological tests are being allowed in American courts. These tests are used in both civil and criminal cases and can have enormous impact. In a criminal case, a psychological test could influence everything from whether the defendant gets bail to their ultimate sentence.

The scientists pored over 876 U.S. court cases that contained psychological evidence and took place between 2016 and 2018. Hundreds of different tests and techniques were entered into the records of these cases — but not all are considered standard in the field.

In order to be admitted into evidence, a test must generally be based on scientific principles and widely accepted in its field. Judges are supposed to keep junk science out of the courts, but they generally do so only when the pseudoscience is challenged by defense attorneys. According to this study, such challenges only occur in less than 3% of cases.

“There’s a lot of stuff that looks like it’s junk and should be filtered out by the courts, but it’s not being filtered out,” said one of the study’s co-authors.

Many tests admitted into evidence have been deemed unreliable

The scientists examined hundreds of psychological and IQ tests that were used in the court cases. They then reviewed the psychological journals to see if these tests could be considered widely accepted.

A third of the tests had never even been reviewed in prominent manuals. Of those that had been reviewed, however, only about 40% received favorable reviews. Almost one quarter had been deemed unreliable. Nevertheless, judges allowed these tests to be used in important court cases like criminal charges and child custody cases.

The good news is that the most common test used in court cases was the Minnesota Multiphasic Personality Inventory, which is widely accepted.

Unfortunately, the second most common test was the Rorschach “ink blot” test first developed in 1921. It does have supporters, but most psychologists consider it dangerously subjective and ambiguous.

One Stanford professor of law and psychology who was not involved in the study told the Associated Press that things have changed since the end of the 1990s. He receives brochures and catalogs advertising new psychological tests, and those used to include information about the clinical validity of the tests. Since the late 1990s, however, that information has disappeared.

Most lawyers and judges are not experts in psychological testing, which makes it hard for them to challenge the admission of pseudoscientific test results. The criminal justice system relies on the field of psychology to self-regulate, which does not appear to be happening, according to the study.



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