the decision to show that the prosecutor really examined the limb of the applicants’ complaint relating to human trafficking”.33 Similarly, in Zoletic, this Court noted that an effective investigation must take place where the “totality” of information constituted an “arguable claim” of treatment prohibited under Article 4.34 15. In S.M. v. Croatia, the Court concluded that the relevant authorities had failed to follow obvious lines of enquiry capable of elucidating the circumstances. Crucially, in that case, the failure to investigate the applicant’s social media interactions, given its use in recruitment by traffickers, was one of the elements considered by the Court in concluding that the State had failed to conduct an effective investigation.35 16. In addition to the requirement of promptness, this Court should be satisfied that the authorities of the Contracting State did not take any rapid decisions leading to a refusal to open criminal proceedings or not to thoroughly investigate without justification and without guaranteeing the safety of potential victims of trafficking.36 17. The intervenors submit that where Contracting State authorities are made aware of potential victims of human trafficking, exploitation or conduct that falls within the scope of Article 4 ECHR, those authorities have an obligation to conduct a thorough and effective investigation. Failing to pursue such an investigation or dismissing complaints with limited investigation would amount to significant flaws under the procedural limb of Article 4 ECHR. This Court is therefore invited to consider whether there is evidence indicating the significant shortcomings of a Contracting State’s attempt to conduct an effective investigation per Article 4.37 II. Article 53 ECHR 18. Article 53 ECHR prohibits a construction of an individual’s Convention rights which would limit the human rights and fundamental freedoms ensured under any other agreement to which the respondent is Party. The Court must construe the rights and freedoms defined in the Convention at least to the level of protection already guaranteed by other international agreements which the respondent state has ratified. a. The Palermo Protocol 19. The Palermo Protocol to Prevent, Suppress and Punish Trafficking in Persons Especially Women and Children requires states to prevent and combat trafficking in human beings, to protect and assist victims and promote cooperation among State Parties. It is noted that, in the absence of a universal instrument on combating trafficking in human beings, these principles will be taken into consideration in the protection of victims and investigation of trafficking in human beings.38 b. UN Convention on the Rights of the Child 20. Of particular relevance in determining compliance with the Osman test39 in relation to a child are the provisions of the UN Convention on the Rights of the Child (‘CRC’) which the UK ratified in 1991.40 The CRC applies to all children under 18 and must 33 ibid., § 119. Zoletic and Others v. Azerbaijan, op. cit., § 193. 35 S.M. v. Croatia [GC], op. cit., § 336-337. 36 M. and Others v. Italy and Bulgaria, no. 40020/03, § 106, 31 July 2012. 37 S.M. v. Croatia [GC], § 345, 346. 38 Palermo Protocol, op. cit., Articles 3, 6, 9, 12. 39 Osman v. the United Kingdom, op. cit., § 116. 40 Despite repeated exhortation from the CRC Committee it has not incorporated it into domestic law, but it is an international obligation binding on the UK and thus binding under Art 53 ECHR. 34 4