A/HRC/10/21 page 4 I. INTRODUCTION 1. The Working Group on Arbitrary Detention was established by the former Commission on Human Rights in its resolution 1991/42 and entrusted with the investigation of instances of alleged arbitrary deprivation of liberty, according to the standards set forth in the Universal Declaration of Human Rights and the relevant international instruments accepted by the States concerned. The mandate of the Working Group was clarified and extended by the Commission in its resolution 1997/50 to cover the issue of administrative custody of asylum-seekers and immigrants. At its sixth session the Human Rights Council assessed the mandate of the Working Group and adopted resolution 6/4, in which it confirmed the scope of its mandate and extended this for a further three-year period. 2. During the period 1 January to 30 April 2008, Ms. Soledad Villagra de Biedermann (Paraguay), Ms. Leïla Zerrougui (Algeria) and Mr. Tamás Bán (Hungary) were members of the Working Group and Ms. Zerrougui was also its Chairperson-Rapporteur. They were replaced on 1 May 2008 by Mr. Roberto Garretón (Chile), Mr. Malick El Hadji Sow (Senegal) and Mr. Aslan Abashidze (Russian Federation), respectively. During the period 1 January to 31 July 2008, Mr. Seyyed Mohammed Hashemi (Islamic Republic of Iran) was also a member of the Working Group. He was replaced on 1 August 2008 by Ms. Shaheen Sardar Ali (Pakistan). 3. On 6 May 2008, Manuela Carmena Castrillo was appointed as Chairperson-Rapporteur of the Working Group and Malick El Hadji Sow was appointed as the Working Group’s Vice-Chairperson. II. ACTIVITIES OF THE WORKING GROUP IN 2008 4. During the period 1 January to 30 November 2008, the Working Group held its fifty-first, fifty-second and fifty-third sessions. It also carried out official missions to Mauritania (19 February-3 March 2008), Colombia (1-10 October 2008), Italy (3-14 November 2008) and Ukraine (22 October-5 November 2008) (see A/HRC/10/21/Add.2-5). A. Handling of communications addressed to the Working Group during 2008 1. Communications transmitted to Governments 5. A description of the cases transmitted and the contents of the replies of Governments will be found in the respective Opinions adopted by the Working Group (A/HRC/10/21/Add.1). 6. During its fifty-first, fifty-second and fifty-third sessions, the Working Group adopted 46 Opinions concerning 183 persons in 22 countries. Some details of the Opinions adopted during these sessions appear in the table below and the complete texts of Opinions Nos. 1/2008 to 16/2008 and 14/2007 to 40/2007 are reproduced in addendum 1 to the present report.