To legally represent clients (generally patent applicants, proprietors and opponents) before the EPO, a patent attorney must first be registered to act in that capacity as a professional representative. To be registered, an individual must qualify as a European patent attorney and, to that end, must pass a written examination, the European Qualifying Examination (EQE). The EQE consists of four papers sat over three days, each day lasting between 5 hours and six and a half hours. Those who enroll for the examination must have an engineering or scientific degree (though long experience in a scientific domain can be sufficient under certain limited conditions), and the candidate must also have practiced under supervision for at least three years in the domain of national or European patent law.