I spent the first two years of my professional life working with people who initially saw me as the devil. These were mothers and fathers who had been ordered by the courts to either come see me or face losing permanent custody of their child, who was already in foster care due to allegations of abuse or neglect. My job as a clinical psychologist was to see whether or not the family was salvageable and, if so, to see if I could help put it back together.
Workplace investigations aren't as adversarial as the court system but they do have some things in common - high stakes, multiple perspectives, and - sometimes -a strong motivation to lie. Two things I've learned from working with people under difficult circumstances - 1) people don't talk to someone they don't trust, and 2) even under the direst circumstances, most people will respond to genuine attempts to understand them. That being said, here are some of the strategies that help me establish rapport when I'm conducting an independent investigation:
Acknowledge the emotions each person is feeling. Each person involved in an investigation has feelings about his or her involvement; the complainant may feel humiliated or scared, the respondent defensive or guilty, and witnesses may be confused or annoyed. Clues to these feelings are found in the way s/he tells his or her story; to ignore them is to ignore the elephant in the room. Acknowledging the emotional tone as well as the content of what someone is saying lets them know you're trying to see things from his/her perspective - regardless of whether or not you agree with it.
Establish your right to be there. You aren't the only one with questions. At the top of the interviewee's list is, "Why should I trust you?" Tell your interviewee why you have the right to be there based on your experience, expertise and empathy. I typically tell interviewees a little bit about my background as a private investigator and psychologist, specifically focusing on my experience as an unbiased, neutral party. If I've done work for the company before, I make sure s/he knows (without, of course, revealing specifics). If the HR person has a good rapport with the interviewee, I might have him or her introduce us. During the interview, I look for shared experiences that might help us connect, whether it's the tough traffic we both experienced driving to work or a common educational experience. In other words, I do whatever I can to let the person know s/he is in good hands.
Show an interest in the person, not just the process. After the introduction, I typically start an interview by asking general questions about the person's day to day job functions or history with the company. If the interviewee has a difficult or unusual name, I ask him or her how to spell it. Yes, I already know the answers to these questions; I've already reviewed personnel files. However, the purpose of these questions is not to get answers; it's to let him or her know I'm interested in him or her as a person, not just in relation to the specifics of the complaint.
Remove physical barriers. There are countless psychological studies that show the unconscious impact physical barriers can have on our ability to connect with another person. Take them out of the equation; don't sit behind a desk and choose a seat that is facing in the same direction as your interviewee. Similarly, think long and hard before putting objects between you and the interviewee; tape recorders often inhibit a person's willingness to speak freely. This is one of the reasons I prefer to take notes instead.
Forget mirroring. I always bristle when I read advice like, "Mimic the other person's body posture and gestures." It sounds so manipulative. Also, can we really be listening to the other person if we're preoccupied with wondering whether enough time has lapsed before we can cross our right leg over our left just like our interviewee has just done? Trust me; if you're really paying attention, your body will automatically communicate this - you'll look the interviewee in the eye, you'll lean forward slightly when the other person is talking, etc.
The Bottom Line
Interviews are the most important part of a workplace investigation and the ability to establish rapport one of the most critical skills. Establish rapport by easing into the interview, acknowledging the emotions as well as the content of what the interviewee is saying. Let him or her know why you have the right to be there and why he or she can trust you to be fair and objective. Make connecting with your interviewee just as important as getting "the truth;" after all, without the former, you won't get to the latter. No one confides in someone s/he dislikes.