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6 Situational and Legal Crime Prevention Practices, Programs, and Policies

This chapter will review the effectiveness of situational and legal crime prevention programs, practices, and policies in reducing crime. Recall from Chapters 3 and 4 that prevention programs have specific delivery requirements and protocols that will be clearly identified in a manual and which must be carefully followed. Programs are typically evaluated using an experiment that compares individuals or groups who receive the program to those who do not (i.e., those in the control condition), with randomized controlled experiments considered the strongest research design. Prevention practices are more general approaches that do not need to be implemented the exact same way every time but rely on similar procedures to prevent crime. These are typically classified as effective following a systematic review or meta‐analysis of multiple evaluations of the approach which indicate that the practice, on average, reduces crime. Finally, prevention policies are legal regulations or formal standards that seek to affect the behavior of a large population. Their effectiveness can be evaluated using experiments or meta‐analyses. We will consider evidence of the effectiveness of all of these types of interventions in this chapter and the other chapters in this section of the textbook.

To be considered effective in reducing crime in this book, programs, practices, and policies have to show a significant impact on rates of crime in rigorous, scientific evaluations which include valid and reliable measures of criminal behavior. When identifying effective crime prevention programs, we will primarily rely upon the recommendations listed on the Blueprints and Coalition websites mentioned in Chapter 5. These sites do not include many practices or policies, especially those related to situational and law enforcement strategies. For this information, we will rely on systematic reviews conducted by the Campbell Collaboration (C2) and CrimeSolutions.gov, as well as reviews conducted for the Centers for Disease Control’s (CDC) Community Guide.

In our view, programs, practices, and policies rated as “Effective with Multiple Studies” by CrimeSolutions.gov have an acceptable level of evidence, comparable to the level required by Blueprints and the Coalition. We will, in most cases, also consider those rated as “Effective” by CrimeSolutions.gov to be effective, since the evidence for practices and some policies is almost always based on meta‐analysis and consideration of multiple studies. However, in our view, programs, practices, and policies rated as “Promising” on the CrimeSolutions.gov website do not meet a high enough standard to be considered effective. We will characterize these types of interventions as having “inconclusive” evidence of effectiveness, meaning that more research is required to demonstrate whether or not they can reduce crime. Policies and practices reviewed by other sources that have had no or few high‐quality evaluations will also be considered as having inconclusive evidence, as will interventions for which the effects on crime are so mixed (with some evaluations showing reductions in crime and others showing no effects) that conclusions about effectiveness cannot be made with certainty. We suspect that the majority of crime prevention efforts that occur every day in communities have inconclusive evidence of effectiveness. Given space limitations, we restrict our identification of inconclusive crime prevention strategies to those that are most commonly used and/or discussed in the crime prevention literature.

While it is important to understand what works to reduce crime, it is just as important to understand what does not work, and ineffective interventions will also be reviewed in this chapter and book. We will classify interventions as ineffective if they have been well evaluated, using the same standards as effective programs, practices, and policies, and shown not to reduce crime. In some cases, ineffective strategies may produce iatrogenic effects, meaning that the program, practice, or policy actually led to an increase in offending. We will identify these types of outcomes when they exist.

In the sections that follow, information about crime prevention strategies is organized according to the type of intervention that has been evaluated. For each type, we begin with a brief description of the approach and its theoretical basis, followed by information on the specific practices, programs, and policies shown to reduce crime using this approach. We will also identify the types of crimes that have been affected, the size of the reduction(s) in crime produced by the intervention and the degree to which the practice, program, or policy is currently being used in communities.

We will identify the amount of change produced by interventions in three ways. First, we may identify the effect size produced by the intervention. Recall from Chapter 4 that effect sizes provide a standardized metric indicating the degree to which an outcome has been changed. In non‐technical terms, effect sizes represent the average change produced by the intervention among the population/area which received it compared to the group/area which did not. Values range from 0 to 1, with larger values indicating larger effects. These figures can be compared across different evaluations since they are on the same scale which is helpful when trying to assess the relative benefits of multiple interventions. In criminology, as in other social sciences, it is rare to see effects anywhere close to 1.0; there are just too many influences that affect criminal behavior. It is common to see small effect sizes, those that are less than 0.20. Effects between 0.21 to 0.40 are considered to be moderate in size, while values greater than 0.40 are considered large (Cohen, 1988).

Second, we will identify changes in crime using odds‐ratios when the outcome is measured with a binary variable that has only two categories of responses, such as whether or not an individual was arrested following the intervention. Odds‐ratios are measured on a scale that includes only positive values. An odds‐ratio that is greater than 1.0 indicates that an increase in the outcome occurred, an odds‐ratio of exactly 1.0 indicates that no change occurred, and an odds‐ratio of less than 1.0 indicates that a decrease in the outcome occurred. Whether or not increases or decreases are desirable depends on how the outcome is coded and how the groups are compared, but we will be sure to let you know if interventions have shown a reduction or increase in crime for those in the intervention compared to the control group. The important thing to remember is that the more the value of the odds‐ratio differs from 1.0, the larger the change in crime.

Third, we may describe the percentage reduction in crime produced by the intervention. This method can be used when outcomes are measured using binary variables or continuous variables, such as when comparing the average number of days that participants spent incarcerated following the intervention. This figure is usually calculated by dividing the outcome achieved in the intervention group by the outcome achieved in the control group, then subtracting that amount from 100. For example, an evaluation of the Behavioral Monitoring and Reinforcement Program (see Chapter 8) found that three of the students who received the intervention had a criminal record, compared to nine of the students in the control group, which is equivalent to a 66% reduction in crime.

Situational Crime Prevention

The goal of situational crime prevention strategies is to make crimes more difficult to commit and more risky for offenders (Clarke, 1995; Eck and Guerette, 2012). These methods do not try to change the offender or the social risk or protective factors associated with individuals’ involvement in crime. Instead, they try to alter the environments in which crimes occur and the immediate, situational factors that provide opportunities for crime. Situational crime prevention began in the UK in the early 1970s when individually focused attempts to rehabilitate offenders seemed to be unsuccessful and difficult to implement. Based on the work of Ronald Clarke and others, the British government began investing in strategies they considered to be more practical and less focused on social influences on crime (Clarke, 1995). Some other European countries and the USA began implementing situational crime prevention in the 1980s.

Situational crime prevention is based, in part, on deterrence theory, which states that offenders will be less likely to break the law if they believe with more certainty that they will be caught doing so. It is also based on rational choice and routine activities theories (Smith and Clarke, 2012). Rational choice theory states that potential offenders consider the risks and benefits of engaging in crime, as well as the amount of effort needed to complete the act and the likelihood of getting caught. They will break the law if the rewards for doing so are greater than the risks and the chances of being detected are seen as small (Clarke and Felson, 1993). For example, installing bullet‐proof barriers between bank tellers and customers and using time‐release safes would be suggested by rational choice theory as an ideal way to prevent bank robberies because those actions would increase the difficulty of the crime, make it seem more risky and reduce its perceived benefits. Routine activities theory states that crime is most likely when there are motivated offenders, few guardians and appealing targets, such as victims who could be physically overpowered or goods which are valuable and easy to steal (Clarke and Felson, 1993). Of these three factors, only the second two are subject to situational crime prevention efforts. Individual factors that may motivate criminal behavior, as well as social risk and protective factors, are assumed to be too difficult to change and too widespread in society. In contrast, increasing guardianship and reducing the attractiveness of targets are considered to be relatively easy and very feasible, and situational crime prevention offers many suggestions for how to make these types of changes in order to reduce opportunities for crime.

These practices can take many different forms and various typologies have been created to organize these different types of actions (e.g., see Smith and Clarke, 2012). Situational crime prevention does not usually involve actions taken by law enforcement, but rather relies on other government officials or private citizens to prevent crime. Involving the general public in crime prevention is seen as a major advantage of situational crime prevention, as doing so can potentially increase the reach of crime prevention in communities and transfer some of the costs otherwise paid for by the general public (through taxes) to individual citizens (Eck, 2003; Eck and Guerette, 2012). Although most situational crime prevention activities are aimed at reducing property offenses, they can prevent personal crimes to the extent that they help protect victims and reduce their encounters with offenders (Lab, 2014).

One over‐arching type of situational crime prevention is place‐based crime prevention (Eck, 2003; Eck and Guerette, 2012). As its name suggests, place‐based prevention occurs in very small geographical areas, such as homes, public buildings, or retail stores. Place‐based prevention can also be used in public transportation facilities such as bus or metro stations or recreational areas like parks and playgrounds. Places are targeted for crime prevention based on information regarding their history of criminal activity. As we will also discuss later in the chapter when reviewing hot spots policing, crime statistics indicate that crimes are not uniformly distributed across geographical areas, but rather tend to occur in the same places at very high rates year after year. Focusing crime prevention activities in these areas can potentially have a large pay‐off.

Place‐based crime prevention includes efforts to increase the guardianship and surveillance of these areas and target hardening practices which make places more difficult to vandalize or burglarize. Common prevention activities intended to increase guardianship are the installation of closed circuit televisions (CCTV), increasing street lighting, and hiring security guards or place managers. As will be true of all situational crime prevention practices discussed in this chapter, all of these strategies are routinely used to prevent crime, but there have been very few rigorous evaluations of their impact on illegal activity. As a result, we currently have inconclusive evidence that increasing guardianship of places reduces crime. Again, this means that such practices may decrease crime or they may not; we just do not have enough information to make such a determination.

Of all the types of situational crime prevention we reviewed, CCTV and street lighting have undergone the most testing and show promise in reducing crime, but the evidence is still inconclusive. CCTV is classified as a Promising practice by CrimeSolutions.gov based on studies showing that its use can reduce property offenses but not violent crimes. Welsh and Farrington (2008a) conducted a meta‐analysis of 41 CCTV evaluations occurring mainly in the UK, with a few studies in the USA, Canada, Sweden, and Norway. Based on all the evaluations, public places that had installed CCTVs experienced small but statistically significant reductions in crime. The average odds‐ratio across studies was 1.19, corresponding to a 16% reduction in criminal behavior in intervention versus comparison areas. However, about half the studies showed no effects on crime and there was no significant decrease in violent crime when considering the 23 studies that evaluated this type of illegal behavior. Furthermore, most of the studies did not involve a rigorous research design.

A more recent randomized evaluation of the impact of CCTV conducted in Philadelphia in the USA had somewhat stronger results. This study showed a 16% reduction in disorder crimes like vandalism and drug sales in areas in which cameras had been installed and a 13% reduction in crime when disorder and violent crimes were combined (Ratcliffe, Taniguchi, and Taylor, 2009). However, there was no impact on violent crime specifically and not all areas with cameras had lower rates of disorder crimes. Given this variation, as well as the mixed results of other studies, Ratcliffe and colleagues (2009) conclude that it is still too soon to advocate for widespread use of CCTVs. There is still too much that is not known about how, where, and why they may work, and more rigorous evaluation of this strategy is needed to answer these questions. We agree with their assessment. Nonetheless, use of CCTV is widespread, particularly in Great Britain. Welsh and Farrington (2008a: 2) note that 170 million pounds were spent by the British federal government on CCTVs in 1999–2001, making it the “single most heavily funded non‐criminal justice [crime prevention] program” in that country. In addition, The Telegraph newspaper in the UK reported in 2013 that there were between 4.9 and 5.9 million CCTVs in that country, or one camera per 11–14 people (Barrett, 2013).

Welsh and Farrington (2008b) have also conducted a meta‐analysis on the impact of street lighting on crime in public areas. Their review was based on 13 studies, none of which were randomized trials. About half the studies conducted in the USA showed that improved lighting was related to fewer crimes, while four of the five studies in the UK showed positive results. Across all studies, crime was reduced by 21% following enhancements to street lighting. Although the authors conclude that street lighting has a significant impact on crime, we consider the methodological rigor of these evaluations as too poor to consider this an effective practice.

Security guards and place managers provide human surveillance of public buildings and other areas. Place managers are those who function as guardians by virtue of their particular position but who are not hired specifically to provide security or surveillance (Welsh, Mudge, and Farrington, 2010). For example, bus drivers may observe and/or prevent passengers’ crimes and parking lot attendants keep watch over the cars residing in public lots. While most public places have guardianship in place, there has been little rigorous evaluation of this practice. We could find only one systematic review that analyzed effects on crime from five studies evaluating the use of security guards and two evaluations of place managers (Welsh et al., 2010). The review found very mixed evidence of effectiveness across studies, with some indicating reductions in crime and some demonstrating no effects. Furthermore, few evaluations involved rigorous methodologies. The lack of research emphasizes the need for more high‐quality studies to determine the effectiveness of this practice (Hollis‐Peel et al., 2011).

There are also few rigorous evaluations of the effectiveness of target hardening practices which make items more difficult to steal or buildings more difficult to break into and/or vandalize. Common target hardening practices include installing locks and engine immobilizers in cars; alarm systems in buildings; metal detectors in airports, schools, and other public buildings; and stronger materials in the construction of payphones, parking meters, doors and windows. Target hardening can also rely on product design and technology to guard against theft or damage (Ekblom, 2012). For example, electronic tags can be used to prevent the theft of clothes, books, and other products. Beer bottles can be designed so that they do not shatter into sharp pieces of glass which could then be used as weapons in a bar fight. And, laptops and phones can be fitted with anti‐virus programs, data encryption programs, and tracking devices that will help protect their data and recover the items if they are stolen. These practices are especially important for objects considered highly susceptible to theft, sometimes referred to as CRAVED products: those that are easily Concealable, Removable, Available, Valuable, Enjoyable, and Disposable (Clarke, 1999).

Comprehensive reviews of this type of situational crime prevention have indicated that many target hardening practices reduce crime (Eck, 2003; Eck and Guerette, 2012; Ekblom, 2012). However, none have strong evidence of effectiveness because, to date, most have not been rigorously evaluated. Almost no randomized evaluations of these practices have been conducted. As Ekblom (2012: 398) states, while there is circumstantial and anecdotal evidence that target hardening works, “the effort to find hard evidence must continue” before we can say that this practice is effective.

One exception to this conclusion may be the use of ignition interlocks in automobiles driven by individuals convicted of driving under the influence (DUI). These devices disable use of a vehicle until the driver provides a breath sample. If the individual’s blood alcohol concentration is lower than a preset level, then the driver is allowed to start the car. Breath samples are collected periodically while the car is in use and the information is logged into a recorder which can be reviewed by those monitoring the offender (Willis, Lybrand, and Bellamy, 2004). Systematic reviews of the effectiveness of this type of target hardening have been conducted for C2 (Willis et al., 2004) and the CDC Community Guide (Elder et al., 2011). Both reviews noted that, compared to those who were not assigned to receive ignition interlocks, drivers whose cars were fitted with ignition interlocks had decreased rates of DUI recidivism during the time that the locks were in the car, with relative reductions ranging from 0.25 to 0.36. However, longer term studies showed that after the locks were removed, there were no significant differences in DUI re‐arrest rates for those who received the locks compared to those who did not. Based on this evidence, both the World Health Organization (2010) and the CDC consider this practice to be effective in reducing DUI offenses while immobilizers are installed in offenders’ cars (Elder et al., 2011).

Two randomized trials conducted in Maryland show longer‐term effects of ignition interlocks. The first study (Beck et al., 1999) involved random assignment to intervention and control groups of mostly White, single males in their early 30s who had committed two or more alcohol‐related traffic offenses in the five years prior to the study. Those in the intervention group were mandated to have locks installed on their cars for one year while those in the control group had their licenses suspended. Consistent with the findings from the meta‐analysis, use of the interlocks was associated with significant differences in re‐arrests at the end of the first year for the intervention versus control group, but no differences were seen one year after the locks were removed. However, there was a significant impact on alcohol traffic violations which favored the intervention group when outcomes were considered across the entire two‐year evaluation period. In the second study (Rauch et al., 2011), significant effects on alcohol‐related traffic violations were shown after two years of mandatory locks, as well as two years later. Across the four‐year study period, alcohol convictions were significantly reduced, by 32%, for the intervention versus control group. Based on these studies, CrimeSolutions.gov rates the use of ignition interlocks as Effective.

Taken as a whole, we consider ignition interlocks to be effective in reducing alcohol‐related traffic offenses in the short term, while the locks are installed in vehicles. However, their ability to produce long‐term changes in offenders’ behavior is still uncertain. Rauch and colleagues (2011) recommend that ignition interlocks be mandated for at least a two‐year period in order to have a sustained effect on drinking and driving. Elder and colleagues (2011) recommend that to have a widespread impact on DUI and alcohol‐related offenses, the use of interlocks must be significantly increased. Although 47 states in the USA have interlock programs, these programs are optional for offenders; they can choose to have ignition locks installed in their vehicles or to have their licenses suspended. Only about 10% of eligible offenders select the interlock option, which means that only a small proportion of the targeted population can hope to benefit from this type of intervention (Elder et al., 2011). Similar barriers to dissemination have been noted in other countries (Willis et al., 2004).

A last type of situational crime prevention used to reduce illegal behavior is Crime Prevention Through Environmental Design (CPTED). This practice was developed in the early 1970s in the USA by criminologist C. Ray Jeffrey and architect Oscar Newman. Although they were not collaborators, they each saw ways to reduce opportunities for criminal behavior by changing the built environment; that is, the physical designs and structures of buildings and neighborhoods. Like other types of situational crime prevention, CPTED aims to increase guardianship and reduce the attractiveness of targets and does not directly intervene with offenders. In CPTED, changes are made to the design of residential or commercial buildings and their surrounding areas in order to increase surveillance and detection of offenders. CPTED would recommend, for example, that home owners remove or trim trees and bushes in order to ensure easy lines of sight in and out of their windows. Likewise, to reduce shoplifting and burglary, stores should be designed with few entries and exits and should clearly mark areas that are off‐limits to customers. CPTED can also be used in city and street planning. For example, dead‐end streets, cul‐de‐sacs and locked gates that bar access to alleyways facing the backs of homes can be used to limit outsiders’ ability to enter neighborhoods. Similarly, street closures and traffic barriers can block entrances to important landmarks in order to prevent vandalism, theft, or terrorist acts. Sometimes these practices are referred to as creating defensible space, meaning that public areas are fortified and strengthened to guard against crime (Newman, 1972).

Defensible space is also considered important in increasing the safety of residential areas (Newman, 1972). For example, fences and gates can be built around individual homes to mark property lines and convey to strangers that the area is private and off‐limits. In addition, housing complexes can be designed such that residents can see each other’s properties, which can increase “natural” surveillance and communicate to would‐be offenders that there is a good chance they will be seen if they commit a crime in the area. Such designs, as well as those used to create common areas where residents can socialize, can also foster territoriality among residents. Territoriality creates a sense of pride and collective ownership among all those living in the housing complex, with the goal of ensuring that all residents will help to control crime in all areas of the property (Mair and Mair, 2003). This concept is similar to that of collective efficacy (Sampson, Raudenbush, and Earls, 1997) from social disorganization theory, which emphasizes the importance of having residents know one another, be aware of strangers who may enter their neighborhoods with the intent to commit crimes and feel a sense of collective ownership of this area so that they work together to prevent crime.

CPTED strategies may also include efforts to remove signs of physical and social disorder from private and/or public property. Such actions are guided by broken windows theory (Wilson and Kelling, 1982), which emphasizes the importance of environmental influences on crime. According to this theory, neighborhoods with an excess of rundown buildings, graffiti, and trash (i.e., physical disorder), as well as homeless persons, prostitution, and open drug‐dealing (i.e., social disorder) are appealing targets for crime. These signs of disorder convey to potential offenders that no one in the area cares if crimes are committed and that if laws are broken, they are unlikely to be apprehended. Conversely, tearing down old buildings and fixing broken windows will help prevent crime and could generate more territoriality, or collective pride and ownership, among residents (Lab, 2014).

Although CPTED is now decades old, rigorous evaluations of CPTED practices, including the creation of defensible space and territoriality, are rare. One review (Casteel and Peek‐Asa, 2000) evaluated whether or not CPTED strategies such as installing CCTVs, hiring security guards, ensuring limited access in and out of buildings and keeping stores well‐lit reduced robberies of public stores. The results indicated that when just one of these types of strategies was used, robberies were not affected. However, when multiple CPTED activities were implemented simultaneously, which was often the case, robberies were reduced from 30% to 85% across studies. Although such effects are fairly large, of the 26 studies considered, most were not published in peer review journals, all but one involved quasi‐experimental research designs, there were few comparisons groups, and most were based on pre/post comparisons with no long‐term analysis of impact (Casteel and Peek‐Asa, 2000).

A separate review of five evaluations of CPTED that involved changes in street design showed some positive effects (Welsh et al., 2010). However, the evaluations were too few in number and of too poor quality to allow conclusions about the effectiveness of this practice. Likewise, strong evidence that reducing physical and social disorder prevents crime is currently lacking, primarily because too few rigorous evaluations of this approach have been conducted (Braga and Bond, 2008). Taken together, these findings indicate that there is currently inconclusive evidence of the effectiveness of CPTED practices. More rigorous research is needed before these types of situational crime prevention can be considered effective in reducing crime.

Considering all that has been discussed, can situational crime prevention practices as a whole be considered effective in reducing crime? Common sense dictates that a home that is well lit, easy to see from the street and protected by a guard dog should be less appealing to burglars compared to a home without these features. Likewise, placing security guards in public places, metal detectors in airports and traffic barriers in front of important landmarks makes sense. But, as we will emphasize throughout this book, basing crime prevention activities on what we think might work is risky. Instead, we want to carefully evaluate whether or not there is strong, scientific evidence that taking an action will reduce crime. Based on this standard, we currently do not have enough evidence to conclude that situational crime prevention practices result in lower rates of crime. As summarized in Table 6.1, the only practice with some evidence of effectiveness is the use of ignition interlocks in vehicles owned or operated by individuals with multiple convictions for alcohol‐related traffic crimes. Even with this practice, however, the evidence suggests that locks are effective in preventing drinking and driving only while installed in vehicles; they do not necessarily produce a sustained change in offenders’ behaviors. All of the other situational crime prevention practices we reviewed have inconclusive evidence of effectiveness. We cannot say with certainty that they reduce, increase or have no impact on crime.

Table 6.1 Effectiveness of situational crime prevention practices.

Several critiques of situational crime prevention have been raised that may explain the uncertainty of their effectiveness. First, although there are some advantages to focusing on the immediate and situational factors that can foster crime, situational crime prevention makes no attempt to change the underlying causes of offending. That is, individual and social risk and protective factors that lead to crime are not addressed by these methods. As such, they may be less able to produce long‐term changes in offending because individuals who may be deterred in the short term from committing a particular offense will likely find an alternative outlet for their illegal activities.

A related second critique is that situational crime prevention does not truly prevent crime, but rather displaces it to another time or location. That is, an offender who encounters guardians and well‐protected targets in one location can simply choose a new target or move to a different location to commit the crime. Clarke (1995) counters this critique by stating that many criminal acts are spontaneous and undertaken after a quick assessment of perceived rewards and risks. If risks are considered to be too large, an individual simply chooses not to commit the act. Most criminals are not so driven to break the law that they will spend a lot of time and effort to commit an offense.

Third, some situational crime prevention practices are considered overly restrictive and intrusive. For example, widespread use of CCTVs in public spaces can infringe upon citizens’ privacy and may provide law enforcement and government too much power (Norris and McCahill, 2006). In addition, building “fortress‐like” homes and housing complexes can lead to isolation of residents and increase fear of crime rather than creating increased ownership, territoriality and security (Lab, 2014).

It is difficult to evaluate the merit of these critiques. Regarding displacement, many studies have not investigated the potential that crime simply “moves around the corner” when situational crime prevention efforts are enacted in particular places (Guerette and Bowers, 2009). The studies that have examined the issue have tended to find little support for displacement. Although displacement of crime to nearby areas sometimes occurs, so does a diffusion of benefits. That is, when crime is decreased by situational crime prevention, surrounding areas that were not directly targeted for prevention often see reductions of crime as well (Guerette and Bowers, 2009; Johnson, Guerette, and Bowers, 2012). While this is promising news, reviews of this literature emphasize that most evaluations of situational crime prevention do not rely on strong research designs, and so their ability to draw conclusions about displacement and diffusion is limited.

It is clear that additional research is needed to evaluate the effectiveness of situational crime prevention strategies. More rigorous evaluation is needed to determine if these efforts work, what types of crimes they are most likely to affect and if changes can be sustained in the long term and with no negative consequences for the public. Given that many situational crime prevention practices are used in combination, more complex research designs will also be required to identify the specific actions or combinations of actions that are most likely to produce reductions in crime.

Law Enforcement Practices

The police do not prevent crime. This is one of the best‐kept secrets of modern life. Experts know it, the police know it, but the public does not know it. Yet the police pretend that they are society’s best defense against crime … This is a myth. First, repeated analysis has consistently failed to find any connection between the number of police officers and crime rates. Secondly, the primary strategies adopted by modern police have been shown to have little or no effect on crime.

Bayley, 1994: 3

Law enforcement practices with evidence of effectiveness

Although crime prevention can be undertaken by anyone, just about every society relies heavily on the police to prevent crime. Law enforcement’s ability to stop law‐breakers is predicted by deterrence theory, which states that the general public and criminals will refrain from illegal behavior when they perceive or actually receive punishments for doing so. Indeed, their mere presence in a neighborhood can stop potential offenders from breaking the law, as predicted by general deterrence, and police do spend considerable time apprehending offenders, which should reduce crime according to specific deterrence.

What does the research say about the ability of law enforcement to prevent crime? As illustrated in the quote by David Bayley, a retired American professor who studied police practices, some criminologists are very skeptical about the potential for law enforcement to effectively reduce and prevent crime. In the 1970s, the prevailing view that “nothing works” in crime prevention applied to most standard law enforcement practices (Telep and Weisburd, 2012; Weisburd and Eck, 2004). For example, there was little evidence that increasing the number of officers on the streets, using random patrols across all parts of a community and ensuring rapid responses to calls for service affected crime rates. We should point out, however, that evaluations of these practices were usually based on poor research designs which made it difficult to draw any firm conclusions about their effectiveness.

In response to this critique, police were forced to become more innovative and consider new methods of law enforcement. They are now more likely to use proactive and preventive approaches, including partnering with local community members to address crime problems (Lab, 2014). They are also more strategic and focused; for example, routine policing practices now involve targeting locally specific causes of crime and more frequently patrolling parts of a city known to have particularly high rates of crime rather than spending equal amounts of time in all areas of the police beat. Are these new strategies any better than the old ones at preventing crime? Are evaluations of these approaches based on more sophisticated research designs than before?

According to reviews of the literature, evaluations of most law enforcement practices still suffer from low methodological rigor and many show mixed evidence of effectiveness. As a result, many commonly used police practices currently have inconclusive evidence of reducing crime, and we are still far from being able to clearly identify “evidence‐based policing strategies” (Sherman, 2011; Weisburd and Eck, 2004). The most promising law enforcement practices are those that (i) are more proactive than reactive, and (ii) focus attention on high crime areas or high‐risk times of day/night rather than using random patrols (Lum, Koper, and Telep, 2011; Sherman and Eck, 2006). Across these different strategies, however, the only policing practice which, in our view, has relatively strong evidence of effectiveness is hot spots policing. (See Table 6.2.)

Table 6.2 Effective law enforcement practices.

Hot spots policing is based on both social disorganization and deterrence theories. Social disorganization theory recognizes that crime is not uniformly distributed across cities but rather clusters in certain geographical areas, typically neighborhoods closest to the city center where rates of poverty are high and social relationships are weak. Hot spots are even smaller geographical areas, usually streets or intersections, in which crime rates are very high and consistently elevated over time. Moreover, these areas account for the majority of crimes in the larger area (Braga, Papachristos, and Hureau, 2012; Lab, 2014). For example, a study of gun crimes in Boston showed that 74% of all shootings taking place from 1980 to 2008 occurred on 5% of street corners; these were Boston’s crime hot spots (Braga, Papachristos, and Hureau, 2010).

In hot spots policing, the first step is for police to identify the high crime areas in their beats, often using crime mapping computer software. They then focus law enforcement activities in these areas, rather than spending equal amounts of time across the entire beat. The specific actions taken in hot spots areas can vary but usually include increased patrol and surveillance, regular “crackdowns” resulting in numerous arrests, and efforts to reduce physical and social disorder. Based on deterrence theory, the greater visibility of police in these places and increased likelihood of arrest will deter potential offenders from breaking the law.

A meta‐analysis of 19 evaluations of hot spots policing showed an average effect size of 0.18, indicating a small but significant reduction in officially recorded crimes (Braga, Papachristos, and Hureau, 2012, 2014). When restricted to the 10 studies that were evaluated using RCTs, the effect size was smaller (0.12) but still statistically significant. Based on this review, CrimeSolutions.gov rates this practice as Effective. It also rates as Effective several studies which evaluated the use of hot spots policing in specific cities (e.g., in Lowell, MA; see: Braga and Bond, 2008; and in Minneapolis, MN; see: Sherman and Weisburd, 1995). Given these reviews, we also consider hot spots policing to be an effective practice.

In a 2008 survey of 176 law enforcement agencies in the USA, 63% said they used hot spots policing to reduce violent crime (Telep and Weisburd, 2012). However, Lum and colleagues (2011) caution that what many police agencies claim to be hot spots policing has more in common with traditional law enforcement strategies such as using random patrols across police beats. As we will discuss in Chapter 11, changing organizational practices to make greater use of evidence‐based prevention strategies is difficult, and law enforcement agencies are no exception.

Law enforcement practices with inconclusive evidence of effectiveness

One challenge with hot spots policing is that, as a general practice, the particular actions that should be taken by police are not specified and may vary across agencies. This diversity makes evaluation difficult and can lead to variation in effects across studies. An even more general law enforcement practice that is specifically intended to take different forms in different agencies is problem‐oriented policing (POP). The goal of POP is to help law enforcement agencies use more strategic, proactive, and locally specific approaches which better address the underlying causes of crime (Lab, 2014; Weisburd and Eck, 2004). In this approach, police are to identify crime problems occurring in their jurisdiction and focus their efforts on these problems and their causes rather than simply reacting to all crimes after they have occurred. In the SARA model, Eck and Spelman (1987) identify four important actions that should occur when departments use POP: (i) Scanning local crime data to identify and prioritize particular problems; (ii) Analyzing the data in order to develop appropriate responses to prioritized problems; (iii) Responding by implementing these responses; and (iv) Assessing the impact of the responses on the targeted problems. This model guides police to use different tactics to address different crimes in different areas under their jurisdiction.

A meta‐analysis of 10 evaluations of POP reported a significant but small average effect on crime of 0.13 (Weisburd et al., 2008, 2010). When considering the four RCTs, the average effect size was similar in size (0.15) and also statistically significant. However, the authors caution that the findings are based on a relatively small number of studies and that the specific law enforcement activities varied across sites, which makes it difficult to determine if some particular responses work better than others. They also noted that some sites reported significant implementation challenges. The assessment phase of the SARA model seems to be particularly challenging for police agencies to complete (Telep and Weisburd, 2012).

The pulling levers police practice combines the problem identification element of POP with a focused deterrence approach that emphasizes certain and severe sanctions for criminal behaviors. As we also describe in Chapter 7, the pulling levers practice is modeled after the Boston Ceasefire project, which showed some positive effects in reducing youth homicides, gun crimes (Braga et al., 2001) and gang‐related shootings (Braga, Hureau, and Papachristos, 2014). In that project, following POP principles, Boston law enforcement officials and their community partners analyzed Boston crime data to determine the types of violent crime which were accounting for the majority of homicides, especially youth homicides, in the city. These data indicated that most homicides were committed by a small number of gang‐involved youth. Based on deterrence theory, the Boston officials decided they needed to send a message to gang members that their future violent crimes would not be tolerated and would be subject to an increased likelihood of arrest, prosecution, and long sentences. This message was communicated in face‐to‐face meetings between law enforcement agents and known gang members, often with participation by local community members (Braga and Weisburd, 2012; Lab, 2014).

Hoping to replicate the findings in Boston, other cities implemented what came to be known as the pulling levers approach. A meta‐analysis of outcomes from 10 of these studies, including the Boston project, indicated an overall effect size of 0.60, reflecting a large impact on crime (Braga and Weisburd, 2012). However, all of the studies were evaluated using QEDs rather than more rigorous designs and not all showed significant crime reductions. Based on this evidence, CrimeSolutions.gov rates pulling levers as a Promising practice. Given the quasi‐experimental nature of the evaluations, we agree with Braga and Weisburd (2014: 574) that “these strategies need to be subjected to more rigorous tests that generate more robust evidence on program impacts.” Until that time, we consider the pulling levers practice to have inconclusive evidence of effectiveness.

Despite the uncertain level of effectiveness, both POP and pulling levers are widely used. Weisburd et al. (2008) report that POP is popular in the UK, and about two‐thirds of large police agencies in the USA reported on a 2007 survey that they “actively encourage problem‐solving” (Telep and Weisburd, 2012). The US Department of Justice has made a significant investment in these practices. It enacted the Strategic Approaches to Community Safety Initiative (SACSI) in the late 1990s, which involved collaboration between US Attorneys and local communities to analyze crime data and create strategic crime prevention plans which could entail pulling levers meetings and cracking down on repeat offenders via increased arrests and prosecution (Lab, 2014; Roehl et al., 2008). A quasi‐experimental evaluation of SACSI based on implementation in 10 cities from 1998 to 2000 showed mixed results across sites in reducing levels of homicide (Roehl et al., 2008; Rosenbaum and Schuck, 2012). Nonetheless, the initiative was expanded to more cities in 2001 in the Project Safe Neighborhoods (PSN) initiative (Lab, 2014). A QED evaluation of PSN in Chicago showed that 24 police beats in Chicago’s West Side which used PSN had significant reductions in homicide, gun homicides, and aggravated assaults compared to 30 beats in the South Side which did not (Papachristos, Meares, and Fagan, 2007). Although this initiative is rated as Promising by CrimeSolutions.gov, a larger QED which compared 82 PSN sites to 170 cities across the country failed to show an overall impact of PSN on crime (McGarrell et al., 2009).

Another policing practice intended to reduce gun crimes is the use of directed patrols. Similar to hot spots policing, but usually focused on larger geographical areas, in this practice, officers increase their patrols of areas known for having elevated levels of gun‐related crime. They may stop more vehicles, make more arrests and confiscate more guns compared to standard policing. Unlike the pulling levers practice, directed patrols are carried out only by law enforcement officers; they do not include collaborations with community members to send general deterrence messages or prosecutors to increase specific deterrence. Of the police practices reviewed here, directed patrols have been evaluated least often. We could find only one review of their effectiveness, which was based on four studies, three conducted in the USA and one in Colombia. Across the four evaluations, 10% to 71% reductions in gun‐related violent crimes and homicides were found in areas using directed patrols (Koper and Mayo‐Wilson, 2012). While suggesting that this practice may work, none of the studies relied on RCTs and strong evidence of effectiveness is not yet available.

The last policing practice we consider to have inconclusive evidence of effectiveness is community‐oriented policing (COP). This practice is similar to POP in emphasizing the use of proactive and preventive measures to address the root causes of crime, rather than reacting to crimes after they occur, and in carefully identifying and prioritizing local crime problems. The main emphasis in COP is the creation of partnerships between law enforcement agents and community residents. To foster communication and collaboration, law enforcement agencies host community meetings to talk to residents about crime issues and collaboratively prioritize the most serious issues to be addressed. In addition, small “storefront” law enforcement stations are placed in neighborhoods where they will be accessible to citizens, and the same officers are assigned to regularly patrol neighborhoods, often on foot, so that residents and officers get to know one another (Lab, 2014). Another key element of COP is the decentralization of police bureaucracy and decision‐making, so that individual officers are more empowered to work with community members (Gill et al., 2014).

A meta‐analysis of studies that defined COP very broadly, as any type of collaboration between police and citizens, found inconclusive evidence of effectiveness for this practice. Based on 25 evaluations, use of COP was associated with odds‐ratios of 1.05 to 1.10, indicating 5% to 10% reductions in crime depending on the specific crimes included in the analysis (Gill et al., 2014). The authors caution that only one study utilized a RCT and that effects were small and inconsistent across studies. Other reviews have failed to show effects of COP in reducing crime and have noted a lack of methodological rigor in most COP evaluations (Lab, 2014; Telep and Weisburd, 2012). In addition, COP is challenging to fully implement; research indicates that many agencies do not implement all parts of this practice, especially decentralization of agencies’ hierarchical structures (Gill et al., 2014; McDonald, 2002).

It should be noted that the review by Gill et al. (2014) did find a significant impact of COP on citizen satisfaction with police officers. This finding is important given highly publicized displays of citizen outrage and displeasure with law enforcement, such as the riots in Ferguson, MO following the shooting of a young African American male by a white police officer. Furthermore, there is some evidence that whether or not people obey the law depends on their perceptions of the legitimacy, fairness, and satisfaction with laws and law enforcement (Tyler, 2004). It is possible then, that COP could have an indirect effect on crime by increasing favorable attitudes towards law enforcement, but this hypothesis has not yet been tested (Gill et al., 2014).

Taking into account the practices reviewed in this section and in the previous section, we conclude that the quote by Bayley is overly pessimistic. We do not have strong evidence that police fail to prevent crime or that the main strategies used by police have little or no impact on offending. Instead, most of the evidence regarding the effectiveness of law enforcement practices is inconclusive, as shown in Table 6.3; we do not yet know with certainty if these actions reduce, increase, or have no effect on crime. As with situational crime prevention, more rigorous evaluation of policing practices is needed to determine if these efforts work and to identify the specific law enforcement activities that are best able to prevent crime.

Table 6.3 Law enforcement practices and policies with inconclusive evidence of effectiveness.

Alcohol‐Related Policies Intended to Prevent Crime

Because drinking alcohol is an illegal behavior for youth and alcohol use by adults has been linked to increased drinking and driving and other criminal behaviors (Anderson, Chisholm, and Fuhr, 2009; Boyum, Caulkins, and Kleiman, 2011), various policies have been enacted to reduce alcohol use and related problems. Alcohol‐related policies include local, state or national ordinances and laws which restrict the supply of or demand for alcohol. They also include the passage and enforcement of laws making driving while intoxicated (DWI) illegal. Such laws are based on general deterrence theory, as they are enacted with the expectation that increasing the certainty and severity of punishments will deter the general population from driving while intoxicated.

DWI studies can examine changes in rates of drinking and driving based on official data, usually police records indicating drivers’ blood alcohol concentration (BAC) levels, or self‐reported data. In addition, they often rely on official records of motor vehicle crashes and/or fatalities, some of which provide information on BAC levels but some of which are “proxy” measures in which the drivers’ BAC is unknown but presumed to be elevated. For example, single‐car accidents occurring at night have been demonstrated as more likely than daytime accidents to be alcohol‐related, so some studies evaluate changes in rates of nighttime, single‐car accidents before and after the passage of a new alcohol‐related law or enforcement strategy (Shults et al., 2001). In order to restrict our review to studies with the most rigorous research methods, we have tried to avoid citing evidence from studies in which actual levels of alcohol use are unknown.

Probably the most well‐known alcohol‐related law, especially among college students, is that establishing a minimum legal drinking age (MLDA). The impact of MLDA laws on both under‐age drinking and drinking and driving has been examined. A meta‐analysis found that about one‐third of 132 MLDA evaluations showed that increasing the minimum drinking age to 21 years in the USA produced statistically significant lower rates of alcohol use by those aged 18 to 20 (Wagenaar and Toomey, 2002). However, about half the studies showed a non‐significant impact of this policy and a few evaluations showed increased rates of drinking. This study and other reviews (Anderson et al., 2009; Gruenewald, 2011; Wagenaar, Lenk, and Toomey, 2005) identify MLDA as an effective policy for reducing under‐age drinking. However, based on the mixed evidence, our interpretation is that there is currently inconclusive evidence of effectiveness for the impact of these laws on under‐age drinking.

There is stronger evidence that MLDA laws produce reductions in under‐age DWI and car crashes. A review of 33 studies conducted by the CDC found that increasing the MLDA reduced alcohol‐related crashes by 18–20‐year‐old drivers by 10% to 16% (Shults et al., 2001). The CDC Community Guide indicates that these results provide “strong evidence” that MLDA laws are effective in preventing alcohol‐related motor vehicle crashes among young adults (Shults et al., 2001: 75), and we agree that there is evidence of effectiveness.

In the USA, all states have set the legal drinking age at 21 years, but some groups, including presidents of some American liberal arts colleges, have lobbied the government to reduce the drinking age (see the Amethyst Initiative website, http://www.theamethystinitiative.org/statement/). In fact, in many other countries the legal drinking age is 18, and New Zealand lowered its age from 20 to 18 years in 1999 (Gruenewald, 2011). Based on the evidence, however, reducing the MLDA is not recommended. The public, at least in the USA, seems to agree. A Gallup poll conducted in 2014 indicated that 74% of respondents aged 18 and older opposed lowering the drinking age to 18 (http://www.gallup.com/poll/174077/lowering‐drinking‐age.aspx).

Local, state, or federal statutes that raise prices or taxes on alcohol are intended to reduce the demand for alcohol by making it more expensive. The effect of this type of policy on under‐age drinking has been evaluated in a systematic review of nine studies conducted mostly in the USA (Elder et al., 2010). In four of the studies, increasing the price of alcohol was significantly associated with less drinking by adolescents and young adults; in the other five studies, a similar pattern was found but not all relationships were statistically significant. In another review, increased pricing was associated with lower rates of youth drinking in 10 of the 13 studies considered, and this association was found in four of the seven high‐quality studies included in the analysis (Wagenaar et al., 2005).

Alcohol pricing has also been shown to affect DWI. Elder and colleagues (2010) found that in two of three studies reviewed, increases in alcohol pricing or taxation were significantly associated with fewer alcohol‐related car crashes and/or fatalities, while five of eight studies relying on proxy measures like nighttime crashes found significant reductions. In addition, two of three other studies showed a relationship between increases in pricing and taxation and lower self‐reported alcohol‐impaired driving. A meta‐analysis of 14 studies examining the impact of alcohol pricing on other types of crime showed that higher pricing was significantly associated with child abuse, violent assaults, and other types of criminal behavior (Wagenaar, Tobler, and Komro, 2010). However, effect sizes were very small for these outcomes (0.02 for child abuse/violence and 0.01 for other crimes).

Based on this research, we conclude that policies which increase the price of alcohol are effective in reducing youth drinking and DWI, but the evidence indicating an impact on other types of crime is inconclusive. Although the USA and most nations impose some taxes on alcohol, the consensus is that taxation tends to be relatively low and has not kept up with inflation (Anderson et al., 2009; Wagenaar et al., 2005). For example, Xu and Chaloupa (2011) report that more than 20 states in the USA have not raised their taxes on beer in the last 20 years and only 10 states have raised beer taxes in the last decade.

Laws can also be passed to prohibit DWI. When first established, such laws did not require evidence that drivers had a certain blood alcohol concentration (BAC) level, but now “per se” laws make it illegal to operate a car when the driver is at or above a certain BAC level (Shults et al., 2001). Different states and nations specify different BAC levels and 19 countries have established lower BACs for young or inexperienced drivers. A CDC evaluation of eight studies assessing the impact of lowering BAC levels from 0.10 to 0.08, which occurred in 21 states in the USA between 1983 and 2001, indicated a median reduction in alcohol‐related motor vehicle fatalities of 7% following this change in law (Shults et al., 2001). The same report analyzed data from six studies, four in the USA and two in Australia, examining the effects of lowering BAC levels to even less than 0.08 for drivers younger than 21 years old (in the USA) or newly licensed drivers (in Australia). All six studies showed reductions in fatal and non‐fatal crashes following the more restrictive laws, ranging from 4% to 24%, results which the CDC considers to be “sufficient evidence” of effectiveness (Shults et al., 2001: 72).

Taken as a whole, these studies demonstrate that legal statutes setting BAC levels are effective in reducing DWI and alcohol‐related car accidents. As of 1995, the federal government in the USA has required states to enact a BAC limit of 0.02 or lower for youth drivers and all have done so (Wagenaar, O’Malley, and LaFond, 2001). Voas and Fell (2011) recommend that the USA lower BAC levels for adult drivers from 0.08 to 0.05, the minimum standard used in Australia, New Zealand, the European Union, and various other countries (for more information on BAC levels internationally, see: www.icap.org). In addition, Wagenaar et al. (2001) recommend that public awareness campaigns be implemented to increase knowledge of BAC laws, given that most youth and adult drivers are unaware of BAC limits.

There is evidence that proactive enforcement of DWI and BAC laws can help reduce alcohol‐impaired driving and related accidents. Although these activities are the responsibility of law enforcement officers, we cover these practices in this section rather than earlier in the chapter given their relationship to alcohol policies. Two different practices have been used to prevent DWI: random breath testing (RBT) and selective breath testing (SBT). When RBT is used, police can regularly stop drivers at random, regardless of whether or not they have been observed to be driving erratically, and require that they submit to a BAC test (Fell, Lacey, and Voas, 2004). This practice is used in Australia and some other European countries but, in the USA, RBT is considered a violation of the Fourth Amendment which prohibits unreasonable searches and seizures. However, a Supreme Court ruling in the Michigan Department of State Police v. Sitz case allowed police to use SBTs to check for alcohol‐impaired drivers. In this practice, police create “sobriety checkpoints” in which they stop all vehicles at a particular location, ask drivers questions, observe their responses and detain those who show signs of alcohol use and impairment (Fell et al., 2004; Shults et al., 2001).

Based on their systemic review of the literature, the CDC has concluded that both RBT and SBT have “strong evidence” of effectiveness in reducing alcohol‐related crashes (Shults et al., 2001: 78). Their analysis of 12 RBT studies indicated median reductions in fatal and non‐fatal crashes of 20% to 24%, while the 11 SBT studies reviewed demonstrated median reductions of 16% to 22%. Other reviews have also identified these practices as effective (Anderson et al., 2009; Voas and Fell, 2011). Because deterrence theory emphasizes that offenders are more likely to be deterred when they are aware of laws and believe that they will be enforced, RBTs and SBTs should be well publicized and frequently conducted. A CDC review of 10 highly publicized SBT programs in the USA showed a median reduction in alcohol‐related crash fatalities of 8.9% (Bergen et al., 2012).

To summarize, there is evidence that a variety of alcohol‐related practices are effective in reducing DWI and alcohol‐related crashes, though impact on under‐age drinking and other crimes is less conclusive, as shown in Table 6.4. Based on this research as a whole, the 2010 World Health Organization’s Global Strategy to Reduce the Harmful Use of Alcohol emphasizes the need for all countries to enact stricter alcohol policies in order to reduce alcohol consumption and problems caused by drinking, such as vehicle crashes and the perpetration of violent crimes (World Health Organization, 2010).1 This report recognizes that most of the evidence for the impact of alcohol‐related policies has been based on studies conducted in English‐speaking and high‐income countries, and that these nations tend to have many alcohol policies already in place. Nonetheless, the report calls for all nations, and especially lower income countries, to take additional steps to reduce the availability and consumption of alcohol and to set and enforce DWI policies. We would add that in the USA, 12 states currently ban SBTs, considering them to violate the Fourth Amendment, and most states have been shown to use sobriety checkpoints less than once per month (Voas and Fell, 2011).

Table 6.4 Effectiveness of alcohol‐related policies.

DWI, driving while intoxicated.

Effectiveness of Other Legal and Criminal Justice Policies Intended to Prevent Crime

In this final section of the chapter, we consider the effectiveness of other legal and criminal justice policies that are enacted locally, in states, or nationally with the intention of preventing crime. Some of these policies are aimed at deterring the general population from committing crime and are based on general deterrence theory. Others are designed to reduce recidivism among those already engaged in crime, with the expectation that legal punishments will reduce future crime by these individuals, as hypothesized by specific deterrence theory. In Chapter 9, we also review the effectiveness of practices and some policies intended to reduce recidivism, but that chapter focuses on interventions implemented in correctional facilities. In this chapter, our discussion focuses on legal statutes making certain behaviors illegal or mandating particular punishments for particular offenses.

Policies with inconclusive evidence of effectiveness

As was true with many of the practices reviewed in this chapter, we lack conclusive evidence regarding the effectiveness of many policies enacted by the criminal justice system to punish offenders, even those that are widely used, as shown in Table 6.5. The uncertainty is largely related to a lack of high‐quality evaluations of these policies. As we will repeat throughout this book, policies of any type are particularly difficult to evaluate using high‐quality research designs. They are often passed by federal or state governments with the expectation that all jurisdictions will comply, such that randomization to intervention and control groups is not possible and suitable comparison groups are difficult to find. Policies can be evaluated using some high‐quality quasi‐experimental research designs, such as time series designs, in which outcomes are assessed before and after a policy has been enacted (Cook and Campbell, 1979; Rossi, Lipsey, and Freeman, 2004). Even with this design, however, it can be difficult to rule out other potential explanations for demonstrated effects (Biglan, Ary, and Wagenaar, 2000).

Table 6.5 Legal and criminal justice policies with inconclusive evidence of effectiveness or shown to be ineffective.

* CrimeSolutions.gov identifies as “Promising” policies intended to reduce gun violence, based on a review of various types of gun‐related practices by Makarios and Pratt (2012).

The first criminal justice policy that has been subject to numerous evaluations but shown to have inconclusive evidence of effectiveness in reducing crime is capital punishment. A report assessing the deterrent effect of capital punishment on homicides, based on studies conducted in the USA, concluded that evaluations of this policy have not been strong enough to provide valid evidence of effectiveness (Nagin and Pepper, 2012). As the authors state: “research to date on the effect of capital punishment on homicides is not informative about whether capital punishment decreases, increases or has no effect on homicide rates” (Nagin and Pepper, 2012: 2). Until additional high‐quality studies are conducted, we cannot say with any certainty whether or not the death penalty reduces homicides.

Three strikes laws also provide harsh punishments for offenders with the goal of reducing their involvement in crime. Three strikes laws mandate increased sentences, sometimes life in prison without parole, for offenders convicted of their third crime, usually a serious felony. These laws were passed in the early 1990s in the USA, when crime rates were increasing and policy‐makers were intent on “getting tough on crime.”

To date, evaluations have not provided a clear indication that three strikes laws reduce crime (Chalfin and McCrary, 2014). In regards to general deterrence, some states have not seen any changes in crime rates following the passage of three strikes policies, while some have seen reductions and other have seen increases (Kovandzic, Sloan, and Vieraitis, 2004). Iatrogenic effects, particularly increases in homicide seen in three strikes states, have been explained as a reaction of criminals to the threat of harsh sanctions that is in opposition to that predicted by deterrence theory. Instead of refraining from committing a third offense, some offenders try to reduce their chances of getting caught for their third strikeable offense by killing witnesses (Kovandzic et al., 2004). On the other hand, some studies have shown that criminals who have already been convicted of two felony crimes and are at risk for three strikes sentencing are less likely to commit a third strikeable offense compared to those whose second crime did not result in a felony conviction (Chalfin and McCrary, 2014). This evidence is more supportive of deterrence theory.

Various gun control policies have also been created based on general and specific deterrence theories. These laws assume that having strict punishments for gun‐related crimes will both deter the general public from committing these offenses and reduce recidivism among criminals who have used weapons during their offenses. Although the general public seems to favor firearms sentencing laws which mandate increased sentence length for gun‐related crimes (Marvell and Moody, 1995), policies intended to reduce the supply of guns are more controversial. For example, proponents of the Second Amendment, which allows American citizens to keep guns in their homes for self‐defense, often oppose policies which restrict the sales of weapons and ammunition, require extensive background checks, or impose waiting times before guns can be purchased. As shown in Figure 6.1, a 2015 Gallup Poll indicated that 47% of Americans favored stricter laws for the sale and purchase of firearms (Swift, 2014). However, this same poll indicated that 73% of citizens did not want handguns to be banned in the USA.

Figure 6.1 The views of American citizens on gun purchase restrictions.

Pro‐gun attitudes among the public and significant lobbying by the National Rifle Association (NRA) and gun manufacturers has led to a very limited body of research evaluating the effects on crime of gun control policies in the USA (American Psychological Association, 2013; Institute of Medicine (IOM) and National Research Council (NRC), 2013). Until very recently, the US Government invested very little funding in gun policy evaluation research and has barred scientific agencies from using federal funds to advocate for gun control. However, in 2013 following the Sandy Hook shooting, President Obama called for stricter gun policies, better implementation and enforcement of current policies and more research on the causes and prevention of gun violence (see the President’s Now is the Time plan, http://www.whitehouse.gov/sites/default/files/docs/wh_now_is_the_time_full.pdf).

Given the limited high‐quality research to date, it is difficult to determine the effectiveness of most gun‐related policies. A meta‐analysis of the impact on crime of various gun laws, nearly all of which were enacted in the USA, showed a significant but small overall effect size of 0.09 (Makarios and Pratt, 2012). Based on this review, CrimeSolutions.gov identifies gun policies as a Promising practice. However, a systematic review of firearms policies conducted by the CDC (Hahn et al., 2005) concluded there is currently insufficient evidence to determine the effectiveness of any particular firearms law, given that high‐quality evaluations of gun policies are rare and findings are mixed across studies. Although the CDC review was not restricted to studies conducted in the USA, nearly all were based on American laws. The World Health Organization emphasizes that information about violent crimes is very difficult to obtain globally and that 60% of countries do not have reliable data even on homicides. This lack of data severely restricts the ability to evaluate the impact on crime of any type of prevention policy including gun laws.

What we don’t know about gun control can hurt us.

Zimring, 1991: 48

When considering specific gun policies, Makarios and Pratt’s (2012) review of studies showed significant effects on crime for both the use of longer prison terms for gun‐related crimes and banning ownership of particular weapons (e.g., high‐capacity assault rifles). However, other comprehensive reviews have indicated that these policies are either ineffective or that there is insufficient evidence to draw conclusions about their effectiveness (Hahn et al., 2005; IOM and NRC, 2013). Research has also shown little evidence of effectiveness for mandatory background checks and waiting periods prior to gun purchase (Hahn et al., 2005; IOM and NRC, 2013; Makarios and Pratt, 2012). These types of policies are unlikely to be effective because many criminals do not purchase guns through legal markets, but rather steal them, buy them on the black market, or receive them from friends or family members.

The CDC has evaluated the impact on crime of shall issue concealed weapons carry laws, which require authorities to issue permits to carry concealed weapons to all applicants who meet background checks (Hahn et al., 2005). Their review found only four evaluations that met their standards, and the results were mixed across studies, leading them to classify these laws as having insufficient evidence of effectiveness.

Evaluations of gun buyback programs in the USA have not been linked to reductions in crime (Braga and Wintemute, 2013; IOM and NRC, 2013; Makarios and Pratt, 2012). There are several explanations for this failure to reduce crime, including that: (i) firearms are widely available in the USA, (ii) most buyback programs collect a very small number of weapons and do not significantly reduce the supply of weapons, (iii) the weapons returned are typically not the types used in crimes, and (iv) participants are usually law‐abiding citizens, not criminals (Braga and Wintemute, 2013). Despite the lack of results in the USA, there is some evidence of effectiveness for gun buyback programs implemented in Australia (Braga and Wintemute, 2013; IOM and NRC, 2013). Following a mass shooting in Tasmania in 1996, the Australian Government banned certain firearms and instituted a national buyback program which resulted in the collection and destruction of about one‐fifth of the total supply of firearms. An analysis of this policy indicated significant reductions in firearm homicides by 2006, which the authors attribute to the greatly reduced access to firearms across the country (Leigh and Neill, 2010).

Specific to youth crime, evaluations of youth curfew laws have shown mixed evidence of success, with participation in crime sometimes increasing, sometimes decreasing and often not changing at all following the adoption of a curfew law (Adams, 2003). As with many policies, however, most evaluations of the impact of curfew laws have not been rigorously conducted. Despite inconclusive evidence of their effectiveness, youth curfews are widely used in communities across the USA. Although the specific restrictions vary across communities, most ban youth under a certain age (typically 16 or 17) from being in public places during specified hours (Adams, 2007).

Ineffective policies

Some policies based on deterrence theory’s hypothesis that harsh sanctions will reduce crime have been demonstrated as ineffective. Evaluations of the impact of transfers or waivers of juvenile offenders to the adult criminal justice system have shown that these policies do not reduce juvenile recidivism. Transfer laws allow offenders under age 18 who have committed particular offenses, usually violent felonies, to be tried in the adult criminal justice system where they are likely to receive harsher sentences. Evaluations indicate that youth who are waived to the adult court are more likely to recidivate than youth who remain in the juvenile justice system. A meta‐analysis of four studies showed a median effect size of 0.34, indicating a medium‐sized increase in arrests for violent and general offenses for youth who received waivers compared to similar offenders who did not (McGowan et al., 2007). These findings have led the CDC to state that policies facilitating the transfer of juveniles to the adult system are not recommended because they are “counterproductive for the purposes of reducing juvenile violence and enhancing public safety” (McGowan et al., 2007: S20). Similarly, a review of six evaluations by OJJPD concluded that transferring juveniles to adult courts “substantially increases recidivism” (Redding, 2010). In response to this evidence, states in the USA are decreasing their use of waivers and sending fewer juvenile offenders to the adult criminal justice system (Brown, 2012).

In terms of adult offenders, there is evidence that arresting individuals for misdemeanor domestic violence offenses does not reduce future domestic violence. An evaluation of this policy conducted in Minneapolis in the 1980s showed evidence of effectiveness, as those who were arrested for domestic violence had lower recidivism rates than offenders who were not arrested (Sherman and Berk, 1984). Consequently, many police departments changed their policies and enacted mandatory arrest policies to be used for domestic violence misdemeanors. However, replications of this project did not produce similarly positive effects (Dunford, Huizinga, and Elliott, 1990; Farrington and Welsh, 2005; Maxwell, Garner, and Fagan, 2002) and the original study failed to show a long‐term impact on recidivism (Sherman and Harris, 2014). Today, the general consensus is that mandatory arrests are not effective in reducing crime (Telep and Weisburd, 2012).2 This example indicates the dangers of making widespread policy changes prior to a careful review of scientific evidence, ideally collected in studies with relatively long follow‐up periods, a subject we will return to in Part IV of this text.

Need for Further Research

The information in this chapter highlights both the breadth of prevention practices and policies that are implemented every day to reduce crime and the lack of strong evidence of effectiveness for many of these interventions. As we will emphasize in this book, many of the most common strategies used to prevent crime have never been well evaluated. As a result, we cannot know with certainty if they reduce, increase, or have no effect on crime. The fact that some preventive interventions actually do increase crime further emphasizes the importance of evaluation. If we want to avoid harming the individuals and public we are trying to protect, then we must rigorously evaluate our crime prevention efforts. As discussed in Chapters 4 and 5 , there is skepticism regarding the usefulness and feasibility of using randomized controlled trials to evaluate criminal justice practices. In fact, some of the most vocal critics of RCTs are advocates of situational crime prevention (e.g., Pawson and Tilley, 1994). Yet, there are many others, including authors of studies reviewed in this chapter, who recognize that use of less rigorous approaches limits our ability to make valid recommendations to policy‐makers and practitioners about how to prevent crime (e.g., Ekblom, 2012). Indeed, there appears to be growing consensus that additional, more rigorous evaluations are needed to determine the effectiveness of situational, law enforcement, and legal crime prevention practices and policies.

Clearly, it will be challenging to conduct these evaluations. Many of the strategies reviewed in this chapter are general practices which can take many different forms. In addition, sometimes multiple strategies are used simultaneously, which makes it difficult to determine if a particular practice is responsible for changes in crime or if it was the combination of actions that produced outcomes. Although situational crime prevention is considered to be relatively easy to implement, many of the law enforcement practices are more difficult to enact, particularly those that involve changes to agency structure and decision‐making processes. All of these issues mean that evaluations must pay close attention to exactly what has been implemented and take this information into account when investigating outcomes.

The quest for a miracle cure for crime and violence sometimes leads to an early or excessive embrace of an unproven technology.

Cook, 2011: 162

While existing practices warrant further evaluation, new strategies are being implemented all the time and their outcomes will also need to be investigated. For example, rapid growth in technology is leading to the creation of many new “hot products” fitting the CRAVED criteria (Clarke, 1999), and new target hardening practices will need to be created and tested to determine if they reduce theft and damage of these products. In terms of policing strategies, recent years have seen many anti‐law enforcement demonstrations and some erosion in the public’s confidence in the police. Given research linking negative views of police to increased law‐breaking, we need to know more about practices which can enhance citizen satisfaction with police, such as community‐policing efforts, and the degree to which better citizen–police relationships lead to reductions in crime.

There is also a need for more evaluation of current and new alcohol‐related and criminal justice policies. The World Health Organization (2010) has called for more evaluation of alcohol policies in low‐ and middle‐income countries as well as greater examination of the impact of such policies on minority and marginalized groups. In the USA, President Obama has called for the implementation and evaluation of stricter gun policies, and it remains to be seen if such legislation will be passed and if new laws will impact gun crime. New policies related to medical and recreational marijuana use also require careful evaluation. We will want to know if these laws impact both juvenile and adult illegal substance use and what impact, if any, they have on other types of crime.

More information about the effectiveness of these approaches will help us come closer to our goal of achieving widespread reductions in crime. Although the practices discussed in this chapter do not try to change the risk and protective factors shown to be related to offending, they can be used in combination with individually focused prevention efforts to ensure that both the immediate and underlying causes of crime are addressed.

Summary

This chapter has reviewed many situational crime prevention practices and legal practices and policies which try to change, respectively, the environmental characteristics that provide opportunities for crime and the ways in which law enforcement and criminal justice agencies interact with potential and/or active offenders. Although commonly used, most of the activities we discussed have inconclusive evidence of effectiveness, largely due to a lack of high‐quality evaluations that can adequately assess their impact on crime. Nearly every study reviewed concluded with a recommendation that the strategy(ies) assessed required more rigorous evaluation.

For example, while there is some indication that increasing guardianship, reducing the attractiveness of targets and changing the physical design of buildings and neighborhoods sometimes reduce crime, none of these situational crime prevention practices has strong enough evidence to suggest that, if widely used in communities, it will have a significant impact on rates of crime. Of the policing practices we considered, hot spots policing was the only method with credible evidence of effectiveness in reducing crime. Practices such as pulling levers, problem‐oriented policing, and community policing have weaker evidence of effectiveness and appear to be challenging for agencies to fully implement.

Legal sanctions can also be used to reduce crime, although not all are successful in meeting this goal. Laws that restrict the availability of alcohol and make it illegal to drive while intoxicated have been shown to reduce rates of DWI, though their impact on under‐age drinking and other types of crime is less certain. Many laws intended to limit the supply and use of guns have inconclusive evidence of effectiveness in reducing crime and require more evaluation. Of the criminal justice policies reviewed, harsh punishments like capital punishment and three strikes laws may or may not reduce adult offending. For juveniles, curfew laws have inconclusive evidence of effectiveness and waiver laws, which transfer juvenile offenders to adult courts, have been shown to increase recidivism.