www.thelancet.com Vol 393 January 19, 2019 287 Security and public health: the interface 2 Law enforcement and public health: recognition and enhancement of joined-up solutions Auke J van Dijk, Victoria Herrington, Nick Crofts, Robert Breunig, Scott Burris, Helen Sullivan, John Middleton, Susan Sherman, Nicholas Thomson Public security and law enforcement have a crucial but often largely unacknowledged role in protecting and promoting public health. Although the security sector is a key partner in many specifc public health programmes, its identity as an important part of the public health endeavour is rarely recognised. This absence of recognition has resulted in a generally inadequate approach to research and investigation of ways in which law enforcement, especially police at both operational and strategic levels, can be efectively engaged to actively promote and protect public health as part of a broader multisectoral public health efort. However, the challenge remains to engage police to consider their role as one that serves a public health function. The challenge consists of overcoming the continuous and competitive demand for police to do so-called policing, rather than serve a broader public health function—often derogatively referred to as social work. This Series paper explores the intersect between law enforcement and public health at the global and local levels and argues that public health is an integral aspect of public safety and security. Recognition of this role of public health is the frst step towards encouraging a joined-up approach to dealing with entrenched social, security, and health issues. Introduction The health of the public requires and is dependent on the safety and security of the individual; therefore, public health as a discipline promotes safety and security. The law exists to promote safety and security and the enforcement of law is part of the same endeavour. The public health and law enforcement sectors should work together with overlapping goals and collaboration to achieve safety and security for populations. The fact that they are often unable to achieve, or inadequately achieve efcient collaboration, even when dealing with the same populations or issues, is to the detriment of both sectors. Although the past few decades have shown an un- precedented growth in collaboration between these sectors, especially in welfare states in developed countries, the collaboration has not led to a unifed political agenda. Consequently, there is a permanent and real risk of returning, perhaps temporarily (but at great cost), to the specialisation perspective of the industrial era, especially considering the trends of austerity and neo-liberal ideology in many developed countries. Increased worries about state security, encompassing mass migration, terrorism, and economic insecurity, could lead to a return to a siloed approach in dealing with problems, emphasising the importance of forging structural collaborations on the basis of interdisciplinary evidence. In this Series paper we focus on high-income countries specifcally. However, developing countries, with their surfeit of complex social problems magnifed by the complications of democratic fragility, have even more to gain from a coherent under- standing and complementarity coordination of law enforcement and public health eforts. At the boundaries of established fields The global population is faced with complex social issues that have an efect on health and criminal justice, including social and economic inequalities; vulnerability to violence, especially gender-based violence in domestic settings; mental health crises; alcohol and drug dependence and related harms such as HIV infection; dementia and expected increases in calls for assistance; and modern slavery and human trafcking. Recognition of the multi- dimensional character of such issues is increasing. The aforementioned issues, particularly violence, alcohol, and Lancet 2019; 393: 287–94 See Comment page 207 This is the second in a Series of two papers about security and public health Police of the Netherlands, The Hague, Amsterdam, Netherlands (A J van Dijk); Australian Institute of Police Management, Sydney, NSW, Australia (V Herrington PhD); Centre for Law Enforcement and Public Health, Amsterdam, Netherlands (Prof N Crofts FAFPHM); Crawford School of Public Policy, Australian National University, Canberra, ACT, Australia (Prof R Breunig PhD, Prof H Sullivan PhD); Center for Public Health Law Research, Temple University, Philadelphia, PA, USA (Prof S Burris JD); Faculty of Public Health, London, UK (Prof J Middleton FFPH); Department of Health, Behavior and Society (Prof S Sherman PhD), and Centre for Public Health and Human Rights (N Thomson PhD), John Hopkins Bloomberg School of Public Health, Baltimore, MD, USA; and Nossal Institute for Global Health (N Thomson), Melbourne School of Population and Global Health (Prof N Crofts), University of Melbourne, Melbourne, VIC, Australia Correspondence to: Dr Victoria Herrington, Australian Institute of Police Management, Sydney, NSW 2095, Australia vherrington@aipm.gov.au Key messages • Both public health and law enforcement are based on a mandate that should ensure a deep level of collaboration across both developed and developing countries to protect the health and safety of the public; these collaborations are inadequate and require improvement • Increased awareness of the complexity of social issues such as violence, mental health, alcohol and drug misuse, migration, and human trafcking should result in the operationalisation of collaborative approaches between law enforcement and public health, but the incentives (and politics) to remain in silos often prevents joined-up approaches • Both sectors need to jointly agree on the best possible societal outcomes and then establish a framework for how each sector can respond and on what performance indicators they will be measured • Evidence shows that both law enforcement and public health sectors are increasingly attempting to conceptualise complex societal issues with a shared aim, but substantial work remains to be done • Interdisciplinary research has an important role to play: articulating indicators and datapoints that can inform both sectors and enhance outcomes for vulnerable populations at which primary eforts of both sectors should be directed Series