A new study of the psychological tests used as evidence in the American legal system has turned up some troubling news. The researchers say many unreliable and beside-the-point tests often help decide people’s fate. And this typically happens without anyone so much as asking whether it is a good idea.
Use of psychological tests in court continues to rise
Judges and juries often hear evidence supposedly based on the science of psychology.
Psychological tests increasingly offer a basis for making countless decisions about people’s fitness to parent, ability to understand charges and tell right from wrong, probability of faking physical or mental symptoms, and much more.
These tests commonly help deny child custody or disability benefits, allow or disallow people to testify or stand trial, or sentence people to prison or death row.
With so much riding on it, you might think the science allowed into court must meet the highest possible standard. If so, the researchers say, you would be wrong.
Looking closely at each test and how cases use it
A team of researchers carefully chose legal standards of fact-finding and relevance from case law and legislation. They also selected reliability and quality standards from the accepted scientific literature.
Finally, they gathered a list of 364 tools used for psychological assessments in real court cases.
Without judging who or what was “bad” or “good,” they still arrived at some troubling results.
Poorly vetted tests often make their way into court
The team found cases used generally accepted tests only 67%, or two thirds, of the time. Of the list of tests named in court cases, only 40% were well respected by authorities in psychological testing, such as the Mental Measurements Yearbook.
The team also found scientific journals had not vetted many tests used in courts, but instead, the tests had been only advertised commercially. Other times, cases misinterpreted tests designed only to gather data about populations of people, using them as if they could give useful evidence about one person in a specific legal case.
Few questions asked about psych tests in court
Some cases did not even specify the tool used for psychological evaluations. Of cases naming the tool, only 5% involved a challenge to whether the tool itself made sense, added relevant information or was fair.
The researchers also found that whether a test was scientifically valid did not seem to affect whether anyone challenged it as evidence.
