We all know the excitement and the feeling of a difficult case coming together. You may have started out with a "who dunnit" and now you are at the point of "I think YOU dunnit!" Evidence has been collected and is being processed, witnesses have provided valuable information, circumstances are pointing you in the direction of Mr. Suspect, and now you have been assigned to question Mr. Suspect about his involvement in this caper.
As you proceed with the interview...keep an open mind. If you go into an interview with the belief that the person is guilty or with the intent to gain a confession or with the thought that the person is going to lie about their involvement, anything the person does or says will be filtered through that belief system, and whatever does not align with it will be discarded or not even perceived! You will look for and find only the things that line up with your belief in the person's guilt, which means you will miss other information the person may be telling you.
The goal in an investigative interview or criminal interrogation is to find the truth, period. By keeping an open mind you are staying open to all of the possibilities, and through your persistent and strategic questioning, those other possibilities will likely be getting eliminated, leading you in the proper direction and case resolution. It is important to take everything into consideration and let the interview and the resulting information lead you to the proper conclusion, not you lead the interview to the conclusion you believe to be correct. Keep an open mind.