rapporteur n : a recorder appointed by a committee to prepare reports of the meetings
Rapporteur (derived from French) is used in international and European legal and political contexts to refer to a person appointed by a deliberative body to investigate an issue or a situation, and report back to that body.
For example, Dick Marty was appointed rapporteur by the Parliamentary Assembly of the Council of Europe to investigate the allegations of extraordinary rendition by the CIA.
Authors of reports prepared by committees of the European Parliament are also known as "rapporteurs". Those persons assisting or helping the rapporteuer are called shadow rapporteur and may vary in numbers depending on the issue.
rapporteur in German: Berichterstatter