Lots of people are confused about the role of an interviewer. Some people think that an interviewer is a Human Resources professional. Human resources is defined as the function within an organization charged managing policies related to the management of individuals who already work in the establishment. The responsibility interviewers perform is the formal meetings for the assessment of the qualifications of an applicant. In other words, interviewers identify future staff.
While the roles of human resource professionals sometimes require them to also perform the duties of an interviewer, this is not essentially part of their job description. People also often confuse interviewers with recruiters or headhunters. Recruiters solicit people to apply for positions. Interviewers select the candidates and determine the finalists for review by management of the company.
If your human resources department is performing interviews, look into additional training to give them the appropriate tools. Nowhere in their education is this job skill addressed.
No one can replace the hiring manager in the interview process.