In my opinion Human Resources should stay out of the hiring process. That should be left to the managers and supervisors that are there to test the candidate’s knowledge.
I have hired employees via the HR system and also have bypassed HR when needed. In all cases, it was left up to the managers/supervisors to test the candidates' knowledge.
From my experience, the final hiring decision usually comes from management anyway. It’s standard practice that HR mainly screens out the bottom rung of applicants who are obviously not qualified for the job they are applying for in the first place. This really does save mid-level managers and upper management the time it would take to complete a basic first screening of resumes anyway. In my experience, management is usually very involved with the hiring process for the business consulting firms I have worked for in the past. HR will ask very basic questions and it really isn’t hard to get past them, plus it really would not be a good use of management time to ask those basic questions when HR can do it for a much cheaper salary rate. When it gets more challenging is when you make it to mid and upper level management, where the questions become more detailed and then you have to complete case studies.