What works to end modern slavery? A review of evidence on policy and interventions

What works to end modern slavery? A review of evidence on policy and interventions

What works to end modern slavery? A review of evidence on policy and interventions

Post and Report by: Katarina Schwarz, Hannah Baumeister, Emily Brady, Sandra Dankova, Naomi Lott, Ana Valverde-Cano, Olivia Wright, and Nesrien Hamid (Delta 8.7 and Rights Lab 2020).


In 2015, United Member States committed to taking action against modern slavery by 2030. Sustainable Development Goal (SDG) Target 8.7 entailed an undertaking by States to:

Take immediate and effective measures to eradicate forced labour, end modern slavery and human trafficking and secure the prohibition and elimination of the worst forms of child labour, including recruitment and use of child soldiers, and by 2025 end child labour in all its forms.

Yet, exactly what constitutes ‘effective measures’ to end these practices remains ambiguous. Although efforts to produce reliable data on antislavery interventions, as well as work to improve access to data, have increased in recent years, the need for a more robust understanding of the current evidence base on ‘what works’ remains. This review provides a snapshot of extant literature, identifying key learnings, trends, and gaps in our understanding of what works in different contexts.

Objectives of the study

The purposes of the study was to examine what is known about effective policy to achieve SDG Target 8.7 in the context of justice, by: (1) collecting and collating existing evidence on what works; (2) identifying the range of claims and hypotheses captured in academic and grey literature, and the evidentiary foundations of these hypotheses; and (3) conducting mixed methods analysis of strengths, weaknesses, and trends in the evidence base. As such, the overarching research question for this study was:

What is known about works at the State and multinational policy level to address modern slavery in the context of justice?

Justice in this context is understood as encompassing criminal justice, civil justice, international justice, survivor engagement and support, and health policy and practice. The study further considers additional cross-cutting themes (applicable in the context of justice, but also in the parallel contexts of markets and crisis), namely gender, education, social policy, and climate and environment. Themes considered in the parallel markets and crisis reviews are also considered in this report.

This study is intended to inform the development of a Policy Guide by Delta 8.7 and the global expert Working Group convened by the United Nations University Centre for Policy Research (UNU-CPR). The Policy Guide is intended to help identify the mix of multilateral and national policies needed to accelerate progress towards SDG 8.7 in the broad policy domain of justice. The Policy Guide is targeted towards an audience of multilateral and national-level policymakers. The review therefore focuses specifically on findings relevant to national and multilateral policy, within the specific area of justice.

Modern slavery

The language of ‘modern slavery’ is used throughout this review, in line with the terminology employed in United Nations Sustainable Development Goal Target 8.7. However, the specific content of definitions of ‘modern slavery’ can differ substantially in different contexts. In most cases, ‘modern slavery’ is conceived as an umbrella term. For markets, these themes were: economic policy; trade policy; financial policy; development policy; and supply chains. For Crisis: conflict; humanitarian contexts; displacement; and migration. What works to address modern slavery? Justice evidence review Return to Contents Return to Hypotheses capturing a range of specific practices within its remit. The International Labour Organisation and Walk Free, for instance, include forced labour and forced marriage in their global estimates of ‘modern slavery’. The UK’s Modern Slavery Act (2015) includes slavery, servitude, forced labour, and trafficking in persons. Australia’s Modern Slavery Act (2018) encompasses slavery, servitude, forced labour, deceptive recruitment for labour or services, forced marriage, trafficking in persons, debt bondage, and the worst forms of child labour. The US Department of State adopts a slightly different approach, suggesting that trafficking in persons and modern slavery are ‘interchangeable umbrella terms’ for the same basic practices (in this case presented as sex trafficking and compelled labour/labour trafficking). However, the US Office to Monitor and Combat Trafficking in Persons also indicates that bonded labour, domestic servitude, and unlawful recruitment and use of child soldiers fall within the remit of forced labour.

While use as an umbrella term is the most commonly adopted approach internationally, some commentators understand ‘modern slavery’ to be a singular and holistic concept—a coherent conceptual category of experience rather than a set. This definition might still encompass a range of different practices, however, ‘modern slavery’ itself is determined by a set of benchmarks specific to the concept, rather than by a finding of another form of exploitation such as forced labour. Kevin Bales, for instance, presents [modern] slavery as defined by a set of core attributes: ‘the state of control exercised over the slave based on violence or its threat, a lack of any payment beyond subsistence, and the theft of the labor or other qualities of the slave for economic gain’. The definition of slavery is therefore presented as ‘a state marked by the loss of free will in which a person is forced through violence or the threat of violence to give up the ability to sell freely his or her own labour power’.

For the purpose of this review, it was not necessary to establish a decisive definition of the concept of ‘modern slavery’. Rather, parameters had to be set as to which evidence would be included as relevant to ‘modern slavery’, and which would be excluded. The research team adopted a broad approach, considering a range of practices associated with modern slavery, as well as sources speaking specifically of ‘modern slavery’ or ‘contemporary slavery’. The range of practices are set out in Annex 1. Search strategy, in Table 1. Term harvesting template.

Summary of findings

The domain area of justice, as defined in this review, is vast. It considers both traditional justice contexts (criminal justice, civil justice, and international justice) and survivor justice—captured in survivor engagement and support, and health policy and practice. It is therefore unsurprising that the issues considered, and approaches adopted, across the 175 records assessed in this study covered significant ground. The 401 distinct claims identified in this review traversed a wide variety of issues, from the role of plea bargaining in cases of online sexual exploitation of children in the Philippines, to need for more robust international guidelines and standards on health policy in the context of modern slavery. They covered issues of international and domestic law and policy, as well as local practice and systemic concerns. They addressed the need for financial support, labour rights, out-of-court settlements, and transnational cooperation agreements. Yet, despite this diversity of content and form, common threads run through many of the studies considered.

Studies addressed what should be done in order to effectively address modern slavery. However, more frequently, they concerned themselves with how these mechanisms and interventions should be delivered, in order to secure positive outcomes for survivors and for the prevention and reduction of modern slavery. They considered the importance of different forms of support for survivors of modern slavery, but more often they considered the particular approaches that must be adopted to facilitate recovery, reintegration, and survivor wellbeing. Thus, long-term, holistic, victimcentred, and survivor-informed support was presented as the framework within which particular services ought to be considered and provided. Studies analysed the importance of robust labour rights and protections for vulnerable populations, but more deeply considered the need for effective monitoring, and enforcement, education, empowerment for workers to assert their rights, and the importance of an overarching commitment to human rights principles. Records highlighted the need for criminal justice accountability, but more often interrogated the importance of victim-centred, evidence-based approaches that support positive engagement with survivors, ensure equal treatment, and avoid criminalising or re-traumatising survivors.

The dominant narrative supported by the evidence collected and considered in this review is therefore that effective measures to address modern slavery in the context of justice demand serious consideration be given to the way in which interventions are delivered, and not only to what measures are adopted. Commitment to evidence-based, victimcentred antislavery efforts requires reflection and dedication to ensuring that policy is translated into practice, and that this practice produces positive outcomes for those experiencing, or vulnerable to, exploitation.

The 36 hypotheses outlined below provide an indication of what is currently known about what works to address modern slavery in the context of criminal justice, civil justice, international justice, survivor engagement and support, and health policy and practice. But they are by no means complete. This review revealed gaps in what is known in core areas of modern slavery response—this requires further review, but more importantly further research underpinned by robust methodologies to ensure findings are meaningful, reliable, and can be extrapolated beyond the scope of the specific inquiry. To take immediate and effective measures to end modern slavery by 2030, more needs to me learned about what works. However, the evidence outlined below provides a useful starting point, and a guide.


This review identified 36 distinct hypotheses about what works to address modern slavery in the context of justice. These are addressed in turn in Section 4. Findings on what works, considered within the theme most dominantly related to the hypothesis. These hypotheses do not represent an exhaustive list of all claims identified in the records assessed, focusing on claims for which authors brought evidence to bear in testing the argument presented. A small number of claims presented in the evidence base that did not find voice across multiple records also remain to be analysed and presented as hypotheses for the final review report. It should further be noted that the records analysed in this review represent a limited cross-section of the wider evidence base (see further Section 2.2. Literature selection). The list of hypotheses below should not, therefore, be taken as an exhaustive list, but as indicative of the evidence base assessed in this review.

The 36 distinct hypotheses about what works to address modern slavery in the context of justice identified in this review are: Hypothesis

1. Providing modern slavery and human trafficking training to law enforcement and criminal justice actors improves identification, investigation, and prosecution of modern slavery offences Hypothesis

2. Cross-sectoral coordination and collaboration between antislavery actors at all levels improves investigations, arrests, and prosecutions Hypothesis

3. Creating specialised law enforcement processes to address modern slavery improves the criminal justice response Hypothesis

4. Ensuring survivors receive appropriate support and criminal justice processes are victim-centred increases victim cooperation with investigations and prosecutions, improving the likelihood of success Hypothesis

5. Robust and specific legislative definitions of modern slavery offences support effective antislavery responses Hypothesis

6. Over-prioritisation of criminal justice mechanisms and responses impedes effective prevention, identification, and support Hypothesis

7. Legal and policy frameworks and practice that ensure survivors are not criminalised for offences committed in connection to their experiences of modern slavery are critical to effective protection and identification Hypothesis

8. Oversight and monitoring mechanisms help ensure effective implementation and enforcement of modern slavery laws and policies Hypothesis

9. Shifting investigation and prosecution strategies away from reliance on survivor testimony to alternative forms of evidence would increase success rates Hypothesis

10. Successful prosecution of modern slavery offences acts as a deterrent to offending Hypothesis

11. Basing policy development on robust evidence improves the effectiveness of antislavery policy Hypothesis

12. Plea bargaining can effectively improve the efficiency of criminal justice processes related to modern slavery

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