Hiring and selection issues are also related to misconduct by law enforcement and I think most people would be surprised at the wide methods of testing and selection of potential police officers.

For example, testing procedures usually include a battery of tests- intelligence, physical exertion tests, mental tests, oral interviews, overall physical health examination, and a criminal background check.  With many of these tests being conducted solely to winnow down the potential pool of applicants for easier hiring selection.

Honestly, there is no rhyme or reason for the variety of methods used by individual organizations.  Each organization picks its own selection process.

For years, researchers have tried to persuade organizations to move away from general aptitude tests and use integrity-based selection methods due to the belief that a person can be taught many things but a person's overall integrity remains consistent throughout life. 

One improvement would be that of truly excellent background examinations.  In my experience, when I was in the US Army and seeking a position that required a Top Secret security clearance, the Defense Department sent an actual person to my hometown to interview people that knew me.  When I was hired by the police department I worked for, the background consisted of a mailed form letter to people I listed as references.  Besides a criminal history review in governmental records, that was it (one of my references also sat in front of me while filling it out asking how certain questions should be answered). 

Now, imagine if a person doing a background check on potential police officers contacted not only listed references but asked those people who the applicant socialized with and who the applicant did not.  Not only that, go back to the person's high school and inquire about how the applicant behaved in high school.  For example, was the person a bully or prone to violence, as well as who did the applicant socialize with (One might have to be careful regarding possible disclosure legalities, still, a form letter is not the answer and one way to get around that may be to require the applicant to sign some sort of disclosure form allowing agencies to do ask things).

And if some sort of human resources stated this would just take too much time and be too expensive, there are two things to consider: one is, what is the alternative, and next, those familiar with police testing know how few people are currently applying for law enforcement jobs (when I tested for my department in 1993 there were something over 600 applicants and since then, I have been told the latest number was around 50).