I read a comment

[wnylib]

12. There are some good psychological tests

that can identify personality traits and qualities that are desirable or undesireable for law enforcement personnel. They could be used for screening applicants. I know of one psych test, the MMPI, that is not possible to cheat on. It is designed to detect lying. I have taken it and it was amazingly accurate. I had to take it as part of the screening process to become a volunteer Big Sister. In addition, I had to have a personal interview with the local director of the program, a home visit by her, a police background check, and 4 written character references.

That's the kind of screening process that LE should use.