There are many key components of conducting an effective interviews and interrogations. Some are vital, some are beneficial, and some are discretionary based upon the individual and the focus of the investigation. One of the components I believe is VITAL to a successful investigative interview or criminal interrogation is establishing your credibility with the individual you are talking with. I view credibility as your "credit level" with another individual. Like a bank, if you have a high credit level, it is more likely you will be trusted with large amounts of money and be granted a loan. If your credit level is low, you will have a difficult time gaining their confidence or trust and you will likely walk out of the bank empty-handed.
Our "credit level" within the context of interviews and interrogations rests on two primary pillars; TRUST and EXPERTISE. This is the foundation of credibility. If we are engaged with the individual about a particular topic, maybe something very sensitive or which may result in punishment of some sort for the individual if the truth came out, we need to have HIGH credibility built upon these pillars in order to be successful.
If we are missing one of these components, this may sabotage the entire interview/interrogation. For instance, if you have the trust of the individual, but you do not show expertise by thorough questioning, having an understanding of the facts of the case, background on the individual, demonstrate a professional and competent demeanor, etc, the individual will be less likely to provide you with the desired information and will be more likely to resist, because he/she KNOWS that their resistance will likely succeed because of your lack of expertise.
On the other hand, if you are extremely competent and have exquisite questioning techniques, you have thoroughly prepared for the interview and have a complete knowledge and understanding of the intricacies of the case and of the individual, and you project professionalism and competence, etc, but you DO NOT HAVE THE TRUST of the individual, you again will likely not succeed in obtaining the desired information. Even though you have high expertise, you need the TRUST of the individual for them to share their biggest "secret".
Think in your own personal life. You may know someone who is a terrific person and you would trust them 100%...with your child, your money, they may take care of your house while you are on vacation, etc. They have your complete TRUST, but you know they do not know ANYTHING about auto mechanics...would you take their advice on car repairs? Probably not.
On the flip-side, if you know someone who is an incredible auto mechanic who has been to the best schools and training, who knows cars inside-and-out, but you found out that he recently was sued for ripping off customers and doing unnecessary repairs on vehicles, would you go to him? Again, probably not. Even though he has the expertise, he does not have your trust.
Thomas Jefferson said, "There is a natural aristocracy amongst men, the grounds of which are virtue and talent."
This is in line with our thinking about credibility; virtue which Thomas Jefferson mentioned relates to the pillar of TRUST (the character) and the talent refers to relates to the pillar of EXPERTISE.
If you wish to be amongst the natural aristocracy when it comes to conducting investigative interviews and criminal interrogations, be sure to have the support of these two "pillars".