Before forensic artists can begin composing police sketches, they obviously need an idea of what their subjects look like. For that reason, the eyewitness interview is the most important step in the police sketch process [source: Taister]. Officers or artists doing the questioning need to understand what to ask and how to approach interviewees to cull the most accurate information, since the human memory for faces can be easily fooled. Often, people have a difficult time recalling specific facial features, and the more time that lapses between a crime and the police sketch interview, the fuzzier those memories become [source: Raeburn].
Depending on the crime and the person being interviewed, police sketch sit-downs can last hours. To get an idea of how these question-and-answer sessions are conducted, consider a 2007 study examining people's ability to describe faces for creating forensics facial composites. It broke down the cognitive interview into three phases: rapport building, free recall and cued recall [source: Frowd et al.].
Rapport building simply involves casual conversation -- "Hi, how are you?" -- in an effort to relax the interviewee. Next, the interviewee is asked to recall as many specific details about the criminal as possible. Often, participants begin by discussing hair and general face shape [source: Frowd et al.]. During the last step, cued recall, the forensic artist will ask the interviewee about any defining features they don't immediately remember. At that point, it might be helpful to jog the interviewee's memory with mug shots of previously incarcerated criminals. That way, seeing a similar nose or eyes or jaw line might spark a flashback. Forensic artists may also keep a catalog of celebrity portraits around since the famous faces can spark visual cues as well [source: Raeburn].
While forensic artists keenly focus on minute facial features, former New York Police Department artist Stephen Manusci notes that victims are more apt to provide broader descriptions, such as a "horse face" or "bug eyes" [source: Lichtman]. The role of an adept artist is to break down, or "decode," those vague generalizations into a collection of discrete facial characteristics. That doesn't mean the forensic artist should ever drill someone for more characteristics; pressuring the interviewee might stifle, rather than stimulate his memory [source: Muench]. As the sketch takes shape, interviewees will also begin to either show recognition or point out discrepancies.