The Special Rapporteur on the promotion and protection of the right to freedom of opinion and expression is an independent expert appointed by the UN Human Rights Council. According to HRC resolution 7/36 the Special Rapporteur is mandated to:
(a) To gather all relevant information, wherever it may occur, relating to violations of the right to freedom of opinion and expression, discrimination against, threats or use of violence, harassment, persecution or intimidation directed at persons seeking to exercise or to promote the exercise of the right to freedom of opinion and expression, including, as a matter of high priority, against journalists or other professionals in the field of information;
(b) To seek, receive and respond to credible and reliable information from Governments, non-governmental organizations and any other parties who have knowledge of these cases;
(c) To make recommendations and provide suggestions on ways and means to better promote and protect the right to freedom of opinion and expression in all its manifestations; and
(d) To contribute to the provision of technical assistance or advisory services by the Office of the United Nations High Commissioner for Human Rights to better promote and protect the right to freedom of opinion and expression.
More information about the mandate can be found at this link.