Every competent investigator knows the importance of communication skills, especially during interviews with a prospective or existing client, witness, suspect, or other party. This is a core competency for the investigator and the skill of questioning and information gathering should never be presumed to exist in the security operative. The art of investigative interview and questioning takes years to perfect. To be a skilled and proficient investigator will demand interrogation and questioning techniques that lead to the truth of both client and cause. These techniques have a cumulative impact on any given case for one source generally leads to another while one lead builds upon another. Nothing in the investigative process is static. As Tom Shamshank observes:

Interview subjects may give a private investigator information that leads to a new interview subject that was not initially included in the investigative plan. Whenever an investigator receives a new lead on a possible interview subject they should always follow up on the lead by conducting background research, contacting the new subject and scheduling and completing an interview. Private investigators should follow the same steps when preparing for, conducting and finalizing a follow-up interview as they would for the initial interview. 1