Reddit reviews Psychological Science in the Courtroom: Consensus and Controversy

(This is from memory, forgive me if a mess up some terminology)

There are Three fundamental problems. Two are psychometric and one is conceptual.

Personality is dimensional. We aren't extroverted or not, we have a level of extroversion varying from low (maybe zero) to high (as in we won't shut the fuck up). The M-B dichotomizes it. It turns the continuum into a binary statement. This cuts out the variability that is required for measuring the variable. The majority of these statistics are based on correlation. Correlation is standardized covariance. Without variance, there's no convariance. If it doesn't vary we can't work out the correlations. This tanks it's test-retest for anyone who isn't at the extreme end of one of the dimensions. This is part of why it is fundamentally unreliable.

Secondly, many of the dimension are bipolar (the continuum is measuring two things, rather than one, as in manic to depressed). Most of the statistics used in psychology assume that you are measuring something that is unipolar. That is, it runs on a continuum from low to high (say from 0-100).

The M-B puts multiple constructs within the same continuum. For example introversion - extroversion. Other personality measures that work (like the NEO-3, or the IPIP) suggest that introversion and extroversion are not the presence or absence of the same thing, but that they are two different constructs. Conceptually, the M-B continuums don't make sense. Are thinking and feeling the opposite of each other? High functioning people tend to do both well, low function people tend to do neither well.

Because the scales in the M-B is running from high to low to high again in something else in this bipolar fashion (think of it as 100 to 0 to 100), they violates the assumptions of most of the statistical tests that would would use to calculate it's basic properties or use it to make judgments about people.

More disconcertingly, it's based on Jungian theory which is more batshit crazy and obsolete that Freud. I can't make that argument as well, because no one bothered to teach me Jung, because noone bothers to teach Jung anymore, for the same reasons we don't teach phrenology. Freud tends to get taught from a historical perspective.

Lilienfeld does at great summary of the research in Psychological Science in the Courtroom. He argues that the four factor version probably meets the Daubert standard, but the 16 factor version does not. I would argue that I really wouldn't want to have to argue making a decision based on it in court.