An interview is a non-accusatory question and answer session with a suspect, victim or witness. The goal of an interview is to gather information and make an assessment of the subject's credibility. Some of this information will be investigative in nature. Examples of investigative questions include, "When did you arrive home last night?"; "Do you have access to a handgun?"; "Do you know who Gloria Smith is?" Other interview questions are specifically designed to elicit behavioral responses from a subject such as, "Do you think this lady really was raped?" or, "Tell me why you wouldn't force a woman to have sex with you?"
It is important that the investigator maintain a non-accusatory tone and demeanor during an interview. This is so even when he knows that the subject has lied to an investigative question or exhibits clear indications of deception to a question designed to evoke behavioral responses. Under this circumstance if the investigator becomes accusatory or challenging the subject will become guarded and reluctant to offer information. A subject will offer much more meaningful information if he does not feel threatened or intimidated. In short an investigator should allow, and in some cases, even invite subjects to lie during an interview. As long as the subject continues to answer the investigator's question information is being learned.
During an interview the investigator should talk about 20% of the time and the person being interviewed 80%. To accomplish this balance, the investigator should keep his questions succinct and, whenever possible, elicit a narrative response from the subject. Too often, investigators reveal so much information through their questions that following an interview the subject has learned much more about the investigation than what the investigator has learned about the suspect's possible involvement in the crime.
The purpose for an interrogation is to elicit the truth from a person whom the investigator believes has lied during an interview. It represents, therefore, an effort to persuade the subject to tell the truth. In some instances, an innocent person will be interrogated. Under this circumstance interrogation tactics used must not be so persuasive as to elicit a false confession. A particular tactic to avoid is to threaten the subject with inevitable consequences followed by a promise of leniency if the subject confesses.
The interrogation should not consist of accusatory questions for this will only lead to further denials from the subject. Rather, it should consist of a monologue during which the investigator makes statements designed to persuade the subject to tell the truth. The monologue often addresses the circumstances which led up to the subject's commission of the crime. In addition, logic and rationale arguments (based on evidence) may be used to persuade the subject to tell the truth.
During an interrogation, the investigator's demeanor should be understanding toward the subject's criminal behavior. It is psychologically much easier for a subject to tell the truth to someone who appears to understand why he committed the crime. At no time should the investigator remind the subject of the seriousness of his offense or possible punishment for it. Such reminders merely reinforce the subject's effort to avoid consequences through continued denials.
If the investigator's persuasive statements have an impact on the subject, the guilty subject often exhibits signs which indicate that he is considering telling the truth. At this point the investigator asks a question which offers the subject two choices concerning some aspect of the crime. For example, "Did you plan this out for months and months in advance or did it pretty much happen on the spur of the moment?" If the subject now acknowledges that the crime happened on the spur of the moment, this represents his initial admission of guilt.
Once the subject makes an initial admission of guilt, active persuasion stops and the investigator returns to the interviewing mode where a full confession is elicited by asking non-accusatory questions. If the subject is truly guilty of the offense he will be able to provide the investigator with details of the crime that only the guilty person would know.
On the other hand, if the investigator makes no clear distinction between interviewing and interrogation, less information will be learned when questions are asked during the interaction that resembles "interviewing" and the persuasive impact of the "interrogation" stage will be minimized. Of most concern, however, is that the guilty subject may never truly be persuaded to reach a stage where he is willing to openly talk about his crime (the first admission of guilt). Under this circumstance, often active persuasion is used to extract details of the confession piece by piece. The voluntariness of that confession, and even its trustworthiness, may later be challenged in court.