Any investigator who is tasked with solving a case must first understand their job is to seek the truth. This may sound obvious, but it deserves mentioning. When interviewing a witness, victim or suspect it is important to understand that how you ask a question may have a significant impact on the answer you receive. Phrasing a question a certain way can strongly influence the response. By mere suggestion it is possible to alter the memory of a subject.
Memory does not work like a video camera. It does not record the information in its entirety. There are different kinds of memory. Episodic memory is that in which we remember an event. This is the type of memory in play during most investigations. When a subject observes an event, the event is encoded into memory. Not every detail gets encoded. Those details can be filled in by the creation of the subject’s own narrative. In other words, he may make up the details or guess. This is where the suggestion of an interviewer may alter the subject’s recollection of events.
Psychologists Elizabeth Loftus and John Palmer conducted an experiment in 1974 to test the level of influence the way a question is asked can have on the response. They asked people to estimate the speed of two vehicles involved in a crash. People are generally not very good at estimating speeds unless they have had specialized training, which is usually reserved for police officers.
The study concluded that the use of harsher descriptions of the accident lead to the witness stating the speeds were higher. When asked how fast the red car was going when it “contacted” the blue car, the witnessed stated the speed to be significantly slower than when the term “smashed” was used in the place of “contacted”. Other terms used were “hit”, “bumped” and “collided”. Each of these terms brought an increased estimation of the speed.
The chart below outlines the affect the descriptive term had on the respondent’s estimation of the speed at the time of the accident.
As you can see, the more intense the description of the accident was, the higher the speed was estimated to be. When “contacted” was used, the average estimated speed was 31 mph. When “smashed” was used, the average response was 41 mph.
Furthermore, those witnesses that were asked the question with the “smashed” term used were far more likely to recall the damage to the vehicles as more severe. In the video the subjects had watched there was no broken glass. In response to the follow up question “Did you see any broken glass?” 16 out of 34 subjects in the “smashed” group stated that they did see broken glass. The control group (they had not been asked about the speed of the cars at the time of the accident) had 44 state no to the broken glass and 6 said yes there was broken glass (see how reliable eyewitness memory is?). Those subjects in the “hit” group had 7 yes responses and 43 no responses. (Loftus and Palmer, 1974)
As this study indicates, it is important to keep your line of questioning as neutral as possible (if the truth is what you are after). Avoid the leading questions. The truth is what the professional investigator is after, and in order to get the truth it is imperative that witness testimony is not tainted with poor or unfair questioning strategies.