Differential police response (DPR) is a management tool that extends the range of options for responding to requests for police service, intended to optimize the match between the service required and the response made. Rather than dispatching a patrol unit to every call, on an as-available basis, police agencies that practice DPR allow for systematically delayed responses by patrol units to some types ofcalls and for “relief” responses, which do not involve a patrol unit, to other types of calls. This practice builds on research that has shown that much of the time an immediate response by patrol units does not improve the prospects for desirable outcomes: the apprehension of suspects, the prevention of injuries, the collection of evidence, or even the satisfaction of callers. Furthermore, the time saved or restructured through the use of DPR is a resource that can be put to more productive uses.
Research in the 1970s and 1980s found that police response time is in most instances unrelated to key outcomes (Kansas City Police Department 1978; Spelman and Brown 1984). Some crimes are ”cold,” having been perpetrated long before they are discovered (thefts from automobiles would be one example), and sometimes the victims of personal crimes (such as a robbery) delay contacting the police, as they assess their situations, decide whether to contact the police, cope with the immediate problems that their victimization has caused, and seek advice or support from friends or family. Thus, even successful efforts by the police to minimize the two components of response time—dispatch time, the lag between receipt of a call and the dispatch of a patrol unit, and travel time, the lag between dispatch and the arrival of the unit at the scene—often cannot have beneficial results. Spelman and Brown (1984) found that a rapid police response was instrumental in apprehending the offender in only 2.9% of reported serious crimes, mainly incidents that were in progress at the time of the call or that were reported with a short delay.
Furthermore, and contrary to the conventional wisdom of police administration, citizen satisfaction with the police response does not turn on response time by itself. Research has shown that citizens’ satisfaction is shaped by the speed of the police response relative to their expectations, and that their expectations are malleable. When citizens expect an immediate response, they tend to be dissatisfied with anything less. But when they are told that police will arrive in thirty minutes (or an hour), and the police do arrive in that time, they tend to be satisfied (Pate et al. 1976; Percy 1980). Citizens are also receptive to relief responses, though not equally receptive to all forms (McEwen, Connors, and Cohen 1986; Worden 1993).
DPR systems may include a number of response options. One of those is a delayed response by patrol units. For any of the types of calls to which a rapid response is not essential—when neither lives nor property are in jeopardy and neither serious offenders nor evidence will van-ish—a dispatcher can place the call in a queue, awaiting the availability of the unit assigned to the beat in which the call originated. Response may be deliberately delayed for thirty minutes, an hour, or longer. Responses to such calls are often delayed even without DPR, but with DPR the delay is by design, and the response protocol specifies that the caller be informed of the likely delay. Other options are relief responses, which divert calls from the patrol dispatch queue altogether. Some kinds of calls may be handled by dispatching nonsworn (civilian) personnel or a sworn specialist (such as community policing officers), while others may be referred to other agencies for assistance.
To other types of requests, callers may be asked to give reports over the phone, to mail a report to the police, to come to the police station to complete a report, to complete a report over the Internet, or to schedule an appointment with a specialist. Reports may be of minor motor vehicle accidents or of minor crimes—typically, offenses in which the loss (for example, from theft) or damage (for example, from vandalism) is under a specified dollar threshold and in which no physical evidence or other leads are available. Research has shown that in such cases, the likelihood of apprehending offenders is very low, and in many departments cases with such low solvability are not even assigned to detectives for follow-up investigation (Greenwood and Petersilia 1975; Eck 1983).
Delayed responses do not save patrol time but reallocate it in what might be more productive ways. A substantial fraction of the time that patrol officers have at their discretion, free of dispatched calls and other administrative assignments, is in blocks that are too small to be put to constructive use. In Indianapolis, for example, one study showed that in a sample of beats 71% of patrol officers’ time was ”unassigned,” but only 44% was unas-signed time in blocks of an hour or more (Mastrofski et al. 1998). The more that dispatchers ”clear their screens” by assigning calls as quickly as possible to the nearest available patrol unit, the more likely that officers’ unassigned time will be fractured into pieces too small for problem solving or other proactive work. When dispatchers are able to ”stack” low-priority calls, however, officers are better able to go out of service to engage in activity at their initiative, uninterrupted by dispatches.
Relief responses save patrol officers the time that they would spend handling the diverted calls, at the cost of the time of the personnel who staff the alternative responses. A field test of DPR in three police departments in the 1980s suggested that 15% to 20% of calls were eligible for relief responses, which could yield net time savings of substantial magnitude (McEwen, Connors, and Cohen 1986). In one department (Garden Grove, California), the eva-luators estimated that alternative responses to selected types of calls could free patrol officers from five hundred hours on dispatched calls each month, while other personnel (for example, telephone report takers) would spend 162 hours handling those diverted calls.
The field test, and other research, also shows that the implementation of DPR is not simple or straightforward. When normal practice provides for dispatching a patrol unit in response to most calls, the information demands at call receipt are minimal: the location, the general nature of the problem, and the identity of the caller. Many police agencies provide for only a small number of call categories (signified by ”10” codes) to characterize the nature of the problem. When DPR is adopted, call takers must gather more information, including not only the nature (and seriousness) of the problem but also when it occurred, whether an offender remains at the scene, and so forth so that they can determine what kind of response is appropriate. Often the information that call takers can obtain is fragmentary or ambiguous. Any doubt about the nature of the response that is required tends to be resolved in favor of dispatching a patrol unit, because mistakes are not symmetrical in their consequences: The consequences of underresponding (for example, referring the call to a telephone report unit when a patrol unit should be dispatched) are potentially much more serious than the consequences of overresponding.
The call classification burden might be eased somewhat if citizens were to play a greater part in differentiating between calls that require an immediate dispatch and calls that do not, especially where this differentiation is facilitated by a 311 system. These systems, designed to field nonemergency calls, emerged in the mid-1990s as an alternative to 911, with the expectation that they would reduce the volume of 911 calls. One study of 311 systems in four cities (focusing primarily on Baltimore) found these expectations fulfilled: Citizen reporting changed dramatically, with the newly established 311 system absorbing about 30% of the calls previously made to 911, and there was widespread community acceptance to using 311 as an alternative number. However, the new system did not have a great impact on policing strategies. Officers continued to be dispatched to all calls (except for priority five), whether the call was placed through 911 or 311. Response times to most categories of 911 calls were the same as before. Further, more than two-thirds of officers surveyed noticed little change in how much discretionary time they had available (Mazerolle et al. 2005).
Police are ”slaves to 911” not only when they run from call to call but also, and much more commonly, when they keep themselves ”in-service”—by doing nothing other than driving around—and available for the next call (Cordner 1982; Kessler 1993). Although some departments actually may be understaffed, in most agencies the deployment of patrol resources is inefficient (Bouza 1990). DPR enables police to meet public demands more economically, and it frees some patrol resources for more productive purposes, including community policing, problem-oriented policing, and other proactive strategies such as directed/aggressive patrol (Worden 1993). Thus, DPR enables police managers to exercise more managerial influence over what their officers do.