Despite the obvious appeal of television police shows, where attractive investigators and their white-smocked laboratory colleagues solve crimes by conducting high-tech computer-assisted analyses of paint samples, cloth fibers, burn patterns, and the like, in fact most crimes are solved by ordinary-looking police who ask victims and witnesses: “What happened?” One of the best predictors of whether police will close a criminal investigation and how the court case will be resolved is the quality of an eyewitness’s report. Furthermore, eyewitness evidence is likely to play a key role for the foreseeable future (Bartol and Bartol, 2004). Indeed, several recent studies have found that police investigators agree that eyewitnesses usually provide central leads in their investigations (Berresheim and Weber, 2003; George and Clifford, 1992; Kebbell and Milne, 1998; Kebbell and Wagstaff, 1997). Unfortunately, however, police also note that witnesses rarely provide sufficient information (Kebbell and Milne, 1998). Ideally, witnesses would observe crimes under optimal viewing conditions, would have detailed and accurate recollections of the crimes, and would voluntarily and accurately communicate these recollections on request. Police cannot control these factors (estimator variables; Wells, 1978), and, as such, they represent more wishful thinking than effective police investigative technique. A more productive approach is to concentrate on those factors that police can control (system variables). Of those, the most important, and the focus of this chapter, is how they interview cooperative witnesses.
