A further difficulty is the fact that the evidence situation often proves to be extremely complicated and the criminal structure is almost impenetrable (cover systems, the international nature and mobility, as well as the great professionalism and group discipline of those involved, tight leadership and merciless penalties against those who break the rules of the group) and the people concerned have effective defences at their disposal (e.g. representation by highly qualified lawyers, political connections).
À cela s'ajoute que la situation en matière de preuve se révèle souvent extrêmement compliquée, que la structure de la criminalité est difficile à saisir (couvertures, internationalité, mobilité, grande professionnalité, discipline de groupe, direction rigoureuse, sanctions impitoyables en cas de non-observance des règles internes) et que les personnes concernées disposent de mécanismes de défense efficaces (par exemple, conseillers juridiques hautement qualifiés, accointances politiques).