From December 1999 to October 2000, Herzog chaired the European Convention which drafted the Charter of Fundamental Rights of the European Union. In January–March 2000, with former central bank President Hans Tietmeyer and former federal judge Paul Kirchhof, Herzog led an independent commission to investigate a financing scandal affecting the CDU. Amid a German debate over the ethics of research in biotechnology and in particular the use of embryos for genetic inquiry and diagnosis, Herzog argued in 2001 that an absolute ban on research on embryonic stem cells – which have the ability to develop into the body's different tissues – would be excessive, stating: "I am not prepared to explain to a child sick with cystic fibrosis, facing death and fighting for breath, the ethical grounds that hinder the science which could save him".