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  • Writer's pictureJerry Ratcliffe

Apples, Oranges and Aircraft Carriers

The following article (Ratcliffe, JH, 2023, Apples, oranges and aircraft carriers: A comment on Weisburd and colleagues, Policing: A Journal of Policy and Practice, 17: 1-3) is behind a paywall, so here is the text of the article.


Apples, Oranges and Aircraft Carriers: A Comment on Weisburd and Colleagues

Jerry H. Ratcliffe

The article by David Weisburd and colleagues reports important findings from a systematic review of the effect of pedestrian stops (with or without an accompanying frisk or search) on crime (using the term ‘SQF’ for stop, question, and frisk). They conclude SQFs ‘were associated with a statistically significant reduction in crime of approximately 13% for intervention areas’. Given the challenge of achieving meaningful crime reduction from any policing strategy, this would normally be cause for celebration.

But they also report in stopped individuals an increase in odds of a mental health issue and negative physical health outcomes, moderate decreases in attitudes favorable to police, and increases in self-reported crime and/or delinquency. While they note there is a high risk of bias in the individual harm studies, they note that there is ‘consistent evidence of negative and substantial harms’ of these stops.

Thus, on the one hand, there are consistent findings of meaningful crime reduction. On the other, excessive stops can be harmful to the individuals who are stopped (notwithstanding the issues of bias in the research).

How is a policy-maker to interpret these findings?

At least in the USA, proactive policing—and especially policing involving traffic and pedestrian stops—has been under intense scrutiny since the 2014 death of Michael Brown in Ferguson, Missouri, and the murder of George Floyd. The authors should be credited for wading into this political quicksand because the metrics in this area are problematic.

Take, for example, what is known in the USA as a Terry Stop, named for the landmark legal ruling of Terry v. Ohio, 392 U.S. 1 (1968), in which an officer can conduct an investigative stop and in certain cases a frisk of outer clothing. Chief Justice Warren, writing the majority opinion of the court, noted ‘where nothing in the initial stages of the encounter serves to dispel [an officer’s] reasonable fear for his own or others’ safety, he is entitled to the protection of himself and others in the area to conduct a carefully limited search of the outer clothing of such persons in an attempt to discover weapons which might be used to assault him’. This suggests the purpose of a Terry Stop is for the immediate protection of the officer and other citizens, and not the aggregate reduction in violent crime within the wider neighborhood. It may be that the measure of success for a Terry Stop is neither the frequency of weapon recovery nor if crime in the wider area declines, but more prosaically that the officer’s reasonable fear was dispelled, and the officer was not seriously injured by a weapon in the interaction. As a metric for ‘success’, community-wide crime reduction is a by-product rather than a goal.

The issue with metrics also plagues the important policy question. Notwithstanding the ‘multiple conceptual and practical difficulties in measuring the cost of crime’ (Manski and Nagin, 2017, p. 9313), cost estimates do exist (Cohen and Bowles, 2010; Heaton, 2010; Mills et al., 2013). But neither physical and mental harm, nor loss of police legitimacy, are estimated in an equivalent manner. Indeed, it may not even be possible to find a comparable gauge.

Weisburd and colleagues note that in the absence of a universal scale, ‘a decision about costs and benefits must by necessity be qualitative and may differ across communities’. This shifts the responsibility to city, community, and police leaders of determining whether the benefits of increased investigative stops outweigh the harms to the individuals. Given the lack of equivalency in the metrics, we are not asking them to compare apples to oranges, but rather apples to aircraft carriers.

Consequently, due to this lack of a common denominator, I’m not sure I would draw the same conclusion that ‘evidence suggests that crime gains will result from proactive SQF programs, but that such gains are likely offset by the negative outcomes found for people who are stopped’. Foot patrol officers in the Philadelphia Foot Patrol Experiment increased recorded pedestrian stops by 64% (Ratcliffe and Sorg, 2017; Ratcliffe et al., 2011); however, their work was associated with a reduction in violent crime of 23%. Is that harm reduction offset by the harm increase among stopped individuals? Hard to say, as victims of violent crime are rarely asked. And murdered people don’t complete surveys.

In the current post-George Floyd world, there is little community support (at least in the USA) for widespread proactive policing, and considerable pressure to reduce the footprint of the police. If that involves sending fewer police to mental health calls for service, then this approach is unlikely to garner much disagreement from police officers (Thacher, 2022). But rolling back on enforcement of the law can have significant negative consequences, as has recently been suggested in Philadelphia (Hogan, 2022).

Weisburd and colleagues summarize that ‘at present, scientific evidence does not support the widespread use of SQFs as a proactive policing strategy’. I would agree but worry that this will be seized on by advocates who deny any value to policing as a blanket rejection of police proactivity and investigative stops. As Sherman (2022, p. 190) notes ‘reducing or suspending patrols in high- crime hot spots may lead to increases in violent crime’, and ‘a steady accumulation of evidence over three decades suggests that proactive prevention activities are more effective in preventing crime than are reactive arrests’ (Lum and Nagin, 2017, p. 342). Removal of investigative stops entirely from the police arsenal would substantially alter the apprehension risk for high-risk offenders and remove any disincentive to carry weapons. This would increase the opportunities for crime. But targeting a reasonable threat of police interdiction can both reduce crime and arrests (Nagin et al., 2015).

The increasing realization that proactive police work and investigative stops have an associated harm that may—or may not—be offset by the gains in public safety is an important step forward. But the work is not yet done. Our goals should be to unlock the formula that allows for low-crime communities to avoid being overpoliced, while recognizing that more precise and targeted proactive work in neighborhoods suffering from rampant violence may be necessary, at least until the threshold for the greater intrusion of police is no longer met. This important article by Weisburd and colleagues brings us closer to the first goal, but the second remains elusive.


Cohen, M. A. and Bowles, R. (2010). ‘Estimating Costs of Crime.’ In Weisburd, D. and Piquero, A. (eds), Handbook of Quantitative Criminology. New York: Springer, pp. 143–162.

Heaton, P. (2010). Hidden in Plain Sight: What Cost- of-Crime Research Can Tell Us About Investing in Police (Occasional paper). Washington, DC: RAND Corporation.

Hogan, T. P. (2022). ‘De-prosecution and Death: A Synthetic Control Analysis of the Impact of De-prosecution on Homicides.’ Criminology and Public Policy 21(3): 489–534. Lum, C. and Nagin, D. S. (2017). ‘Reinventing American Policing.’ Crime and Justice 46(1): 339–393.

Manski, C. F. and Nagin, D. S. (2017). ‘Assessing Benefits, Costs, and Disparate Racial Impacts of Confrontational Proactive Policing.’ PNAS 114(15): 9308–9313.

Mills, H., Skodbo, S., and Blyth, P. (2013). Understanding Organised Crime: Estimating the Scale and the Social and Economic Costs (No. 73). London: Home Office.

Nagin, D. S., Solow, R., and Lum, C. (2015). ‘Deterrence, Criminal Opportunities and the Police.’ Criminology 53(1): 74–100.

Ratcliffe, J. H. and Sorg, E. T. (2017). Foot Patrol: Rethinking the Cornerstone of Policing. New York: Springer (Criminology Briefs).

Ratcliffe, J. H., Taniguchi, T., Groff, E. R., and Wood, J.D. (2011). ‘The Philadelphia Foot Patrol Experiment: A Randomized Controlled Trial of Police Patrol Effectiveness in Violent Crime Hotspots.’ Criminology 49(3): 795–831.

Sherman, L. W. (2022). ‘Goldilocks and the Three ‘Ts’: Targeting, Testing, and Tracking for ‘Just Right’ Democratic Policing.’ Criminology & Public Policy 21(1): 175–196.

Thacher, D. (2022). ‘Shrinking the Police Footprint.’ Criminal Justice Ethics 41(1): 62–85.

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