The interview environment, the interviewer's behavior, and the questions posed by the interviewer all contain potential factors that can cause or prevent contamination. Regarding the interview environment, the selection of a quiet place that is free of distractions and without any physical barriers between the interviewer and the subject of the interview is critically important. The use of one interviewer is the preferred protocol, but if two investigators are present, one should take the lead in the interview while the other investigator takes notes or assesses the subject's verbal and nonverbal behavior. No physical barriers, such as a desk or even an object such as a drinking glass or an ashtray, should be between the interviewer and the subject, so there will be no symbolic object where the subject can hide. Further, the interviewer's verbal and nonverbal cues can encourage or discourage the suspect's sharing of complete and accurate information. Interviewers should maintain an open posture without crossing their arms, be frontally aligned and facing the subject, lean forward to show interest in what the subject is saying, and acknowledge what is said by maintaining consistent eye contact while nodding their heads to encourage the subject to continue speaking. The suspect should not be interrupted when he is speaking. An interviewer's voice can also affect the outcome of the interview, especially during the information-gathering stage. Interviewers should consciously slow their rate of speech and speak softly. Loud and abrasive voice tones are sure to cause the subject to shut down and adopt a defensive and deceptive posture. Regarding the questions posed to the subject, they should encourage subjects to participate in the interview process and stimulate the flow of information. Interviewers should begin the information-gathering phase with broad open-ended inquiries designed to obtain as much information as possible. From the information gained in this phase, direct and specific closed questions can be posed. Interviewers should carefully consider their choice of words for questions asked. The wording of the question should not suggest a preferred answer. If subjects do not perceive a question as a threat or as a means of answering in such a way as to please the interviewer, then more complete and accurate responses are likely to be forthcoming. Examples of appropriate and inappropriate wording of questions are provided. 46 notes