During an investigation, you may need to question many types of witnesses such as victims, accusers, complainants, and informants. Your choice of questioning technique will be based not on the type of witness, but on the attitude and willingness of the witness to provide the information being sought. Expect to encounter difficulty when interviewing a person who resents authority, regards the interview as inconvenient and fears self-involvement.

Although physical evidence often plays a key role in an investigation, it has been consistently true that the most prolific and valuable sources of information are the people involved. The skilled investigator recognizes that human factors strongly influence the success or failure of an interview. Human factors include such variables as fear, reluctance, prejudice, revenge, hate, and love. An investigator who can figure out the variables and adjust the approach accordingly will excel at interviewing.

The complex motivations of people cause questioning to be an art rather than a science. Recognizing the subtle signals sent out by a witness is the first step on the path leading to truth. More important than anything else is an ability to correctly assess what the interviewee wants, what he/she is afraid of, and what is going on inside the person’s head. This is not an easy task. Performing the task well is founded on a base of knowledge sharpened through training and practice. Ideally, the investigator will know basic psychology and be a keen observer of persons.

In addition to the obstacles mentioned above are the witnesses’perception, memory, stress and prejudice. Perception is conditioned by the abilities to see, hear, smell, taste, and touch. Perception is also affected by the location of the viewer in relation to the incident, the amount of time intervening between occurrence and interview, and the nature of events that occur during the interval between occurrence and interview.

Because memory erodes over time, interviews should be conducted as quickly as practicable. Memory not only fades; it becomes colored, either consciously or unconsciously by what the witness was exposed to after the incident. Remarks made by other witnesses or newspaper accounts may cause an interviewee to fill in the gaps of personal memory with details about which he/she has no direct knowledge. A witness may even form a personal opinion of guilt or innocence and shape testimony accordingly. This possibility is reduced when the interview is conducted soon, that is, before the witness has time to form personal judgments that distort the truth.

A person subjected to stressful, exciting, or injurious events after observing an incident is likely to forget details. To illustrate, assume a pedestrian observes a speeding motorist strike another pedestrian and drive away from the scene. The witness is caught up in a series of actions in which he or she might render first aid and transport the injured victim to the hospital. What the witness experienced in the immediate aftermath may cause a faulty recollection concerning the hit and run vehicle.

It is not unreasonable to expect every witness to be prejudiced to some degree. The strength and targets of prejudice vary among people. You should be alert to prejudice and deal with it when it surfaces. One way to keep information from being distorted by prejudice is to require detailed, specific answers. If allowed to talk in generalities, a prejudiced person will make statements that are partially accurate and partially misleading. By remaining within a narrow line of discussion aimed at a specific issue, you force the witness to respond with information free of bias.