The personnel who carry out on-site investigation mainly include investigators, supervisors and heads of investigation departments. Before on-site investigation, the above-mentioned personnel must receive different levels of training, especially for interviewers and supervisors.

Training is divided into general skills, skill training and project training. In order to control the interviewer's mistakes and deception, the supervisor usually pays a return visit to the interviewer in a certain proportion according to the plan after the interview to confirm whether the investigation has really been carried out and whether the investigation has been carried out according to the planned procedures.