The front page of today's Wall Street Journal (subscription required) has a lengthy article about the most widely used personality test, the Minnesota Multiphasic Personality Inventory (MMPI). The focus of the story is about a specialty sub-scale developed by Dr. Paul Lees-Haley called the "fake-bad" scale which is used to detect malingering. While the focus of the WSJ piece is on the scale's increased use in personal injury lawsuits, it is also used in criminal matters as well.

It's safe to assume that much will be said by the professional mental health field in the coming days about this story. Among those comments will be the maxim that the MMPI is "just one piece of data" used in determining psychological states among litigants and defendants. This is surely true, but the reliance (perhaps even over-reliance) by some forensic psychologists on personality measures as lie detectors often gives these tests more weight than they deserve.

Update: Ted Frank at Point of Law has some brief thoughts as well. While I agree with Ted that there is indeed some peer review research behind the scale, there are good reasons to be wary of bubble sheet forms that are proffered as measures of deception. It's not so much that these measures can't measure deception, rather they can be easily abused by experts who use them irresponsibly.