Better evidence for a better world

Campbell evidence and gap maps

Coming soon – Campbell EGMs are a new evidence synthesis product. Plain language summaries of our EGMs will be published on this website. The interactive EGMs and full EGM reports will be available in our journal on the Wiley Online Library platform: click here.

Learn more about Campbell EGMs

Campbell-partnered EGMs

Campbell has produced maps on other topics, sometimes in partnership with other organisations.

See the Campbell-partnered EGMs
Search Result: 48 Records found
Page 3 of 5


Interview and interrogation methods and their effects on investigative outcomes
  • Authors Christian Meissner, Allison Redlich, Sujeeta Bhatt, Susan Brandon
  • Published date 2012-09-01
  • Coordinating group(s) Crime and Justice
  • Type of document Review User abstract
  • Title Interview and interrogation methods and their effects on investigative outcomes
  • See the full review
  • English

    Information-gathering method elicits true confessions

    Police interrogations may result in false confessions, as has been documented in many countries. Findings from this systematic review indicate that the information-gathering method of questioning suspects increases the chance of getting a true confession and reduces the chance of forcing a false confession.

    Interrogation methods in police investigations

    The interrogation of suspects can be very important to securing convictions of guilty parties and freeing the innocent. There are two general methods of questioning suspects: information-gathering and accusatorial. The information-gathering approach is used in the United Kingdom, New Zealand, Australia, and Western Europe. It is characterized by rapport-building, truth-seeking, and active listening. The accusatorial approach is used primarily in the United States and Canada. It is characterized by accusation, confrontation, psychological manipulation, and the disallowing of denials. There is much controversy over which method is more effective.

    Confessions in context

    The results of this systematic review indicate that both accusatorial and information- gathering methods of interrogation are effective tools for obtaining confessions in a real- world context. Importantly, studies of real-life contexts do not separate the outcomes according to innocent and guilty suspects. In other words, the outcome measured is the number of confessions. No analysis is provided on how many are true and false.

    In experimental contexts, results indicate that both methods increase the odds of obtaining a true confession from a guilty participant. When compared with a control condition, however, the accusatorial method also increases the likelihood of inducing innocent participants to make a confession. The information gathering-method, on the other hand, reduces the chance of obtaining false confessions.

    Facts about the systematic review

    The aim of this review was to examine the impact of accusatorial versus information- gathering approaches on the elicitation of confessions. The authors conducted two meta- analytic reviews that included: 1) observational and quasi-experimental field studies of actual suspects in which the guilt/innocence of the suspect was unknown, and; 2) experimental, laboratory-based studies in which the guilt/innocence of the suspect was known.

    Five field studies and 12 experimental studies from the USA (12), UK (4) and Canada (1) were identified. The field studies included 1) at least one coded and quantified interviewing/interrogation method and 2) data on confession outcomes tied to the questioning style. All included experimental studies involved 1) at least two distinct interviewing styles (e.g., direct questioning and accusatorial approach) and 2) sufficient data on true and/or false confession outcomes.

    The findings suggest the superiority of information-gathering methods in the interrogative context. Given that the number of participants in these studies is relatively small, these findings should be interpreted with caution.

The effects of stress management interventions among police officers and recruits
  • Authors George Patterson, Irene Chung, Philip G Swan
  • Published date 2012-04-18
  • Coordinating group(s) Crime and Justice
  • Type of document Review
  • Title The effects of stress management interventions among police officers and recruits
  • See the full review
Drug courts' effects on criminal offending for juveniles and adults
  • Authors Ojmarrh Mitchell, David Wilson, Amy Eggers, Doris MacKenzie
  • Published date 2012-02-02
  • Coordinating group(s) Crime and Justice
  • Type of document Review Plain language summary
  • Title Drug courts' effects on criminal offending for juveniles and adults
  • Library Image Library Image
  • See the full review
  • Records available in English, Spanish
  • English


    Drug courts: more effective in reducing drug use and reoffending in adults than juveniles

    Drug courts monitor drug-involved offenders’ abstinence from drug use through frequent drug testing and compliance with drug treatment programs. These courts are effective in reducing future offending and drug use (recidivism) for adults, but not for juveniles.

    What did the review study?

    Drug courts are an alternative to the traditional justice system. Drug-involved offenders are offered entry into drug court with an agreement that the charges against them will be reduced if they complete a treatment program.

    Participants’ adherence to the program is monitored by the court. Various rewards (e.g., praise, tokens of achievement, movement to the next phase of the program) and sanctions (e.g., increased treatment attendance or urine testing, short jail stays) are used to compel compliance to program requirements.

    This review examines the effectiveness of drug courts, including drug courts for juvenile and drunk driving (DWI) offenders, in reducing recidivism compared to the standard justice system. The review critically assesses these courts’ effects on recidivism in the short and long term. It also assesses the methodological soundness of the existing evidence, as well as the relationship between drug court features and effectiveness.

    What studies are included?

    Included studies are evaluations of drug courts that used an experimental and quasi-experimental comparison group design. Studies must also have had an outcome that examined criminal or drug-use behavior (recidivism).

    A total of 154 studies were included in the review which, of which 92 focused on adult drug courts, 34 on juvenile drug courts, and 28 on drunk driving courts.

    What are the main results in this review?

    There is a large, significant mean average effect from both adult and DWI drug courts. Overall, recidivism rates were just over one third (38 per cent) for programme participants, compared to half (50 per cent) for comparable nonparticipants. This effect endures for at least three years.

    There is a smaller effect from juvenile drug courts. Program participation reduces recidivism from 50% to 44%.

    The effects of drug court participation are highly variable. Programs with fewer high-risk offenders are more effective in reducing reoffending rates. This finding may help explain why juvenile courts are less effective, as they deal with a greater proportion of high-risk offenders.

    Variation in intensity of programs is not related to effectiveness. Courts that required more than the standard number of phases or drug tests were no more effective than other courts.

    The highest quality evidence from three experimental evaluations confirms the impact from adult courts on recidivism, though there was some inconsistency in durability of the effects over time. For DWI drug courts three of the four experimental evaluations produced similar results as the adult drug courts, but one high quality study found negative effects.

    What do the findings in this review mean?

    Drug courts appear to be effective in reducing recidivism for adults and drunk driving. There is a smaller effect for juveniles, which may be due to the fact that they deal with a greater proportion of high-risk offenders.

    But further experimental research would be useful to confirm the effects of DWI courts, and to examine the variation in effects to identify what sort of drug courts and in which contexts.

  • Spanish

    Click on 'Download PDF' on the right to view the plain language summary in Spanish.

Police strategies for reducing illegal possession and carrying of firearms
  • Authors Christopher Koper, Evan Mayo-Wilson
  • Published date 2012-01-09
  • Coordinating group(s) Crime and Justice
  • Type of document Review
  • Title Police strategies for reducing illegal possession and carrying of firearms
  • See the full review
Cross-border trafficking in human beings: prevention and intervention strategies for reducing sexual exploitation
  • Authors Peter Van Der Laan, Monika Smit, Inge Busschers, Pauline Aarten
  • Published date 2011-12-01
  • Coordinating group(s) Crime and Justice
  • Type of document Review User abstract
  • Title Cross-border trafficking in human beings: prevention and intervention strategies for reducing sexual exploitation
  • See the full review
Use of DNA testing in police investigative work for increasing offender identification, arrest, conviction and case clearance
  • Authors David Wilson, David Weisburd, Dave McClure
  • Published date 2011-09-12
  • Coordinating group(s) Crime and Justice
  • Type of document Review User abstract
  • Title Use of DNA testing in police investigative work for increasing offender identification, arrest, conviction and case clearance
  • See the full review
  • English

    Caught red handed: DNA testing improves case outcomes

    DNA testing has been increasingly used as part of police investigative work since the 1980s. Initially used only in rape and homicide cases, its use has now expanded to other crimes such as property offenses. The evidence suggests that DNA testing can improve outcomes of police investigations. The findings of a systematic Campbell review of research findings are set out below.

    The evolution of DNA use in police investigations

    The rate of solving crimes has historically been low and this has created interest in supplementing traditional investigative techniques. DNA testing is no longer used only to match evidence from a crime scene to an identified suspect. The development of national DNA databases makes it possible to identify suspects based on DNA samples before there is any other evidence implicating the individual. This opens up the possibility of using DNA testing as a part of routine police investigative practices. While DNA testing is expensive and time-consuming, the science behind DNA testing is considered sound.

    The utility of DNA testing in routine police investigation: beyond a reasonable doubt?

    This review examines whether the use of DNA testing improves the effectiveness of police in identifying and convicting criminals. It found evidence to suggest that including DNA testing in routine police practice is helpful when investigating a broad range of crimes. This conclusion must be qualified, as the majority of the evidence comes from studies with clear methodological weaknesses. The single high quality study included in this review provides compelling evidence for the value of DNA testing in solving high-value property crimes; DNA

    testing more than tripled the odds of identifying a suspect and making an arrest, and more than doubled the odds of a case being accepted for prosecution.

    Facts about the systematic review

    This review looked at seven outcomes: the effects on the apprehension of criminals, reductions in the likelihood of arresting/prosecuting innocent people, and the effect of DNA on the cost, speed, clearance rates, arrest rates and conviction rates of investigations. All five of the included studies explicitly aimed to assess the impact of DNA testing on the success of police investigations. Given the diversity of designs, the authors did not meta-analyze results across studies. Meta-analysis was done within two multi-site studies and showed positive results regarding the identification, arrest and prosecution of criminals and increased sentence length and chance of pleas bargains. No evidence was found on speed of investigations.

    Only one study addressed the cost effectiveness of DNA testing: the average cost of adding DNA testing to property crime investigations ranged from just under $2,000 USD to

    $13,000USD. The price of DNA testing continues to drop as a result of technological advances and economies of scale. The cost also depends on the type of DNA analysis conducted.

    Other research in the area

    Additional high quality evaluations – and particularly random-assignment evaluations - are needed to establish the robustness and generalizability of these findings.

Spatial displacement and diffusion of benefits among geographically-focused policing initiatives
  • Authors Kate Bowers, Shane Johnson, Rob Guerette, Lucia Summers, Suzanne Poynton
  • Published date 2011-06-15
  • Coordinating group(s) Crime and Justice
  • Type of document Review User abstract
  • Title Spatial displacement and diffusion of benefits among geographically-focused policing initiatives
  • See the full review
  • English

    Benefits of crime fighting are contagious

    What happens to surrounding neighborhoods when more police are put in high crime areas? Do criminals just move to nearby neighborhoods or do the crime-fighting benefits spread? A systematic review of international research finds that increasing police presence in problem areas not only reduces crime in those areas, but can also lead to less crime in nearby areas.

    Side effects of focused policing: displacement or diffusion

    A common criticism of focused policing efforts (such as hotspots policing, ‘crackdowns’, or problem-oriented policing) is that it does not address the root causes of crime; criminals just move to another neighborhood. This is known as ‘crime displacement’. Criminal activity can in fact shift in a number of different ways. It can move from one neighborhood to another, the time of day crime occurs can change, different targets may be chosen, how the crime is commited may change (e.g. breaking windows versus picking locks). There can be changes in the type of offences committed and in the people engaging in crime (new offenders replace old). In theory, these kinds of changes in criminal activity can cancel out the benefits of increased police efforts in problem areas.

    It has also been argued, however, that increasing police presence in one area can have positive effects for nearby areas. There can be a ‘bonus effect’ of a reduction in crime in nearby neighborhoods.

    It is important to consider both negative and positive side effects of focused policing when deciding on policing strategies.

    Focused policing has diffuse benefits

    The main findings of this review indicate that initiatives to increase police presence in problem areas are linked to less crime and disorder. Moreover, although there are no significant changes to nearby neighborhoods, the results show a trend towards the spread of crime-fighting benefits.

    The findings of this review have implications for criminological theory. They support the idea that different areas in a city offer better or worse opportunities to commit crime. If it were equally easy (and worthwhile) to steal or murder in all areas of a city, criminals would likely just move away from the area with more police to the next neighborhood. But this is not the case; some neighborhoods seem to offer more and easier chances to commit crime. This means that increasing police in those areas can be a powerful method in combating crime.

    Facts about the systematic review

    This review includes 44 studies. The majority of the studies are from the USA (30) but studies from the United Kingdom (10) Sweden (3) and Australia (1) are also included. Each study evaluates a focused policing intervention which was limited to a physical area (smaller than a city/region), uses some quantitative measure of crime, and reports original research findings. The studies evaluate a broad range of interventions implemented in different contexts, including Problem-Orientated Policing (12), Police Crackdowns (10), Police Patrols (7), Community-oriented policing (5) and Hotspot policing (4).

    This review focuses on two primary outcomes: the effect of focused policing on crime levels in the target neighborhood; and the effect of focused policing on nearby neighborhoods. A meta-analysis of sixteen studies to examine the effect on the target neighborhood shows that focused policing reduces crime in the target neighborhood.

    The evidence also indicates that when focused policing is implemented, crime levels change in nearby areas more than would be expected if there was no focused policing in the target neighbourhood. The weight of the evidence shows that crime is reduced in these areas. This suggests that focused policing is more likely to result in a spread of crime control benefit than simply moving criminals to the closest neighbourhood.

Motivational interviewing for substance abuse
  • Authors Geir Smedslund, Rigmor C. Berg, Karianne Thune Hammerstrøm, Asbjørn Steiro, Kari Ann Leiknes, Helene Marie Dahl, Kjetil Karlsen
  • Published date 2011-04-08
  • Coordinating group(s) Crime and Justice
  • Type of document Review
  • Title Motivational interviewing for substance abuse
  • See the full review
Formal system processing of juveniles: effects on delinquency
  • Authors Anthony Petrosino, Sarah Guckenburg, Carolyn Turpin-Petrosino
  • Published date 2010-03-10
  • Coordinating group(s) Crime and Justice
  • Type of document Review
  • Title Formal system processing of juveniles: effects on delinquency
  • See the full review
Self-control interventions for children under 10 for improving self-control and delinquency and problem behaviors
  • Authors Alex R. Piquero, Wesley G. Jennings, David P. Farrington
  • Published date 2010-03-09
  • Coordinating group(s) Crime and Justice
  • Type of document Review User abstract
  • Title Self-control interventions for children under 10 for improving self-control and delinquency and problem behaviors
  • See the full review
  • English

    Children should learn self-control

    This scenario will be familiar to many: a screaming child, out of control by the candy shelves in the supermarket. The child was refused a piece of candy. New research indicates that intervening against this type of behaviour pays off. Teaching children self-control at an early age can prevent antisocial behaviour and delinquency later on. This is what a new Campbell systematic review of the most robust international research results in the area shows.

    Low self-control can have serious consequences

    As early as around the age of three, children should be able to show internal self- control and refrain from doing things they have been told not to do. However, not all children learn self-control. On the contrary, many children have problems e.g. containing emotions and acting on sudden impulses.

    Self-control is an interesting personal attribute. According to the recognised General Theory of Crime by Gottfredson and Hirschi, antisocial behaviour and delinquency are the results of low self-control. As opposed to people who have a high degree of self-control, and who are able to control their behaviour and restrain from sudden impulses and emotional reactions, people with low self-control are far more spontaneous. They are much more emotionally expressive and react spontaneously on their own impulses and sudden ideas. Six characteristics in particular are typical in people with low self-control: impulsivity and inability to delay gratification; lack of persistence, tenacity or diligence; partaking in novelty or risk-seeking activities; little value of intellectual ability; self-centredness; and a volatile temper. According to the theory, these traits are why children with low self-control will be prone to taking part in criminal activity and antisocial activity. Moreover, research experience demonstrates that self-control is learned in the early years of life and is difficult to change later on.

    This Campbell systematic review sets out to examine whether programmes aimed at teaching children self-control (self-control improvement programmes) have an effect.

    Important to learn social skills

    'Self-control improvement programmes' is a generic term for the various different programmes which, in this systematic review, aim at children up to the age of ten. The majority of the programmes included in the review are based on a form of social skills training. Social skills training focuses in particular on communication: to be able to express oneself and communicate one’s thoughts, needs and feelings; and to be better at reacting to and understanding other people’s thoughts, needs, and feelings. The idea is that these skills will help children avoid and/or tackle unpleasant situations.

    One example of a method used is the Control Signal Poster, which uses a traffic-light approach. The teacher uses a poster of a set of traffic lights: Red = Stop and calm down. Yellow = Slow down and think of a plan. Green = Go and try the plan. The children learn not to act on their direct impulse when they get frustrated, for example while playing in the school yard or when doing their homework. They learn instead to go to the red light, stop, and think before they act. They also learn to put the situation and their feelings into words and thus identify the problem, before proceeding to the yellow light. Here, they consider the possible solutions and select the best one. The next step is the green light, namely testing their plan and then evaluating whether it has worked. If the plan does not work, the child will have to go through all of steps again to solve the problem and will ultimately end up having found the best way to tackle the given situation.

    Teaching children self-control pays off

    The systematic review is based on the best of the available studies examining the effect of self-control improvement programmes aimed at children. The outcome is clear: the programmes successfully improve children’s self-control. Furthermore, they reduce children’s antisocial behaviour and delinquency.

    This tells us that teaching children better self-control at an early age pays off. Rather than throwing money at expensive sanctioning policies, the authors of the systematic review recommend that priority is given to preventive work and self- control improvement efforts. Self-control improvement programmes aimed at children can be a good investment, if the aim is to prevent antisocial behaviour and petty crime.

    About the systematic review

    • This review includes 34 studies covering a total of 4,386 children, aged from to 10 years.
    • Of these, 31 studies are from the US, 2 are from Canada and 1 is from Israel.
    • The review covers a time span of 33 years (1975-2008).
    • The children studied were 6.23 years old on average, lived in low-income areas, and were recruited via their schools.
    • Included were only studies using randomized controlled trial design with post test measures of self-control and/or child behaviour problems for the experimental and control participants.
    • Studies with mentally and/or physically handicapped subjects were not included.
    • Both published and unpublished studies were included, however only studies available in English.
    • Outcomes were collected reports from parents and/or teachers, clinical reports, direct observation and/or reports from the children themselves.


Page 3 of 5

Contact us