EVERY person before they committed an alleged crime was a straightforward, upright person. Before the cop turned bad and was on the take, the exec looted the company, the teacher baffled the coed, the caregiver ripped off the senior client or the EMT worker touched the patient inappropriately, etc. they all checked out and would pass the garden variety background check. Background checks are in reality no better than the last flight inspection, it is no real guarantee the aircraft will even make it off the tarmac, but it is all one has to go on. There might be ways to make people more honest that might border on science fiction, but for the sake of safety no one will want to give up that much control or have others tinkering with their thinking….so…we get what we get.