My master's thesis was about determining scientific properties of some formalized tests and checklists. It was a lot of work and I realized how difficult it is to achieve a truly reliable test. Of course, the most important thing is to remove the bias of the tester. That can never happen in a legal situation because its all about be adversarial. Bias is built into it!

The only people who should administer tests are those who have no stake in the outcome. But, that is not how it works in the legal system either, because the "expert" is being paid by one side or the other, aren't they?

Also, if you have ever known someone who was truly a psychopath, they are unlikely to expose themselves in a testing situation. Even a very experienced tester can think they were "nice as pie." That's part of the issue.

I suspect a lot of people are wrongly identified as psychopaths, mostly due to invalid assumptions made by people who don't know what they are actually looking at.