Granted, there are far more good cops than bad, but the bad still get through.
Teachers have the same issue, they all get a Psych test to be certified, how many terrible teachers have you come across. More than I care to think about
again: what happens with the information when someone FAILS this "test" does the government use this information later? What happens if later you get in a bar fight? will this information come back to haunt you???