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2: What are the origins of evidence-based policy?

This chapter starts by exploring the development of evidence-based policy in two non-policing areas: medicine and aviation. The history of medical science is noticeable for key studies where experiments have demonstrated the value in overcoming confirmation bias. Aviation safety has made progress through incremental learning, and the adoption of techniques that reduce complexity, such as pilot checklists. These policy lessons for policing are discussed, alongside an outline of the emergence of evidence-based policing. The basic principles of an evidence-based approach, along with four different types of policing evidence, round out the chapter.

Glossary terms in this chapter

Comparison group: A comparison group or areas are as equivalent as possible to the treatment or intervention group in an experiment, except they do not receive the treatment. Comparison groups/areas tell you what might have happened if the initiative had not occurred.

Confirmation bias: Our human tendency to interpret information and evidence in a way that supports our existing beliefs.

Checklist: A list of items that require checking, verification, action, or inspection, and is usually performed in a certain order. 

Field experiment: A field experiment is a research study that uses experimental methods, not in a laboratory, but in a natural setting.

Data tracking: The frequent or continuous monitoring of specific data points to indicate what, where and when people and systems are performing activities related to specific objectives.

Scientific evidence: Scientific evidence is the accumulated wisdom from systematic studies and observations that can help a policy maker reach a conclusion about a policy choice. Scientific evidence (at least in the context of this book) is proof that can support a position or claim of effectiveness.

Organizational evidence: Data and information derived from organizational records, internal reports and files. 

Professional evidence: As with clinical experience, the combination of experience, training, and judgement exercised in a practical or professional setting by police officers, if studied and documented in a systematic manner.

Stakeholder evidence: Knowledge derived from stakeholders with a stake or investment in the workings of police or the outcomes of police activity. Stakeholders often include local community members, politicians, and personnel in related fields such as public health workers.

Additional information and links

Evidence-based medicine

The chapter starts by discussing evidence-based medicine. There is a nice definition of this from the National Cancer Institute

The story of James Lind is well covered by the marvelous James Lind Library. It has a range of resources far beyond that of James Lind. It has an interesting coverage of key moments in evidence-based medical history. 

Western histories tend to emphasize key figures in western science; however, Abū Bakr Muḥammad ibn Zakariyyāʾ al-Rāzī is a major name in the history of the Islamic medical tradition. The Stanford Encyclopedia of Philosophy has an excellent page covering the history of the fascinating character.

While he was chief resident at the Vienna General Hospital, Ignaz Semmelweis was Hungarian. This may explain why he ran into problems with the administration of his hospital. His life story is both fascinating and tragic. His key contribution is the handwashing discussed in the chapter. For more context, there is a seven-minute NPR audio story that is worth a listen. 

Aviation safety

The story of the Wright brothers is nicely covered at this page

The Boeing model 299 has a good historical story at the National Museum of the United States Air Force

Atul Gawande's best-selling book "The Checklist Manifesto" is a longer read than necessary, but has pretty much everything you might want to know about checklists. And it is less than ten bucks at Amazon

The accident involving Allegiant Air flight 436 is not generally well covered, though FlightGlobal has an article that goes into this non-fatal accident in some detail. 

The emergence of evidence in policing

The definitive report about the Kansas City Preventative Patrol Experiment is available from the National Policing Institute.

The National Policing Institute also has a summary report of the Newark Foot Patrol Experiment

A summary of the Minneapolis Domestic Violence Experiment is nicely covered by the same organization. 

And of course the key summary of evidence-based policing was written by Lawrence Sherman in 1998 for the then Police Foundation, now called the National Policing Institute. 

Rather than being a 1970s progressive rock band, the Evidence-Based Policymaking Collaborative is - at the time of writing - not present on the internet. 

The source for the PANDA crime reduction model is a recent, previous book, Reducing Crime: A Companion for Police Leaders. Details can be found at

Reducing Crime podcast episode

Rob Briner (#11)

Rob Briner is Professor of Organizational Psychology in the School of Business and Management at Queen Mary University of London. He tells me about the vital role of accountability in pushing evidence-based practice, the appeal of apparent simplicity and good intentions that can trap people in harmful responses, the three words managers can't seem to say, and the idea of watchful waiting.

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